text: /*
   * 'OpenSSL for Ruby' project
   * Copyright (C) 2000-2002  GOTOU Yuuzou <gotoyuzo@notwork.org>
   * Copyright (C) 2001-2002  Michal Rokos <m.rokos@sh.cvut.cz>
   * Copyright (C) 2001-2007  Technorama Ltd. <oss-ruby@technorama.net>
   * All rights reserved.
   */
  /*
   * This program is licensed under the same licence as Ruby.
   * (See the file 'LICENCE'.)
   */
  #include "ossl.h"
  
  #define numberof(ary) (int)(sizeof(ary)/sizeof((ary)[0]))
  
  #ifdef _WIN32
  #  define TO_SOCKET(s) _get_osfhandle(s)
  #else
  #  define TO_SOCKET(s) (s)
  #endif
  
  #define GetSSLCTX(obj, ctx) do { \
  	TypedData_Get_Struct((obj), SSL_CTX, &ossl_sslctx_type, (ctx));	\
  } while (0)
  
  VALUE mSSL;
  static VALUE mSSLExtConfig;
  static VALUE eSSLError;
  VALUE cSSLContext;
  VALUE cSSLSocket;
  
  static VALUE eSSLErrorWaitReadable;
  static VALUE eSSLErrorWaitWritable;
  
  static ID id_call, ID_callback_state, id_tmp_dh_callback,
  	  id_npn_protocols_encoded;
  static VALUE sym_exception, sym_wait_readable, sym_wait_writable;
  
  static ID id_i_cert_store, id_i_ca_file, id_i_ca_path, id_i_verify_mode,
  	  id_i_verify_depth, id_i_verify_callback, id_i_client_ca,
  	  id_i_renegotiation_cb, id_i_cert, id_i_key, id_i_extra_chain_cert,
  	  id_i_client_cert_cb, id_i_timeout,
  	  id_i_session_id_context, id_i_session_get_cb, id_i_session_new_cb,
  	  id_i_session_remove_cb, id_i_npn_select_cb, id_i_npn_protocols,
  	  id_i_alpn_select_cb, id_i_alpn_protocols, id_i_servername_cb,
  	  id_i_verify_hostname;
  static ID id_i_io, id_i_context, id_i_hostname;
  
  static int ossl_ssl_ex_vcb_idx;
  static int ossl_ssl_ex_ptr_idx;
  static int ossl_sslctx_ex_ptr_idx;
  #if !defined(HAVE_X509_STORE_UP_REF)
  static int ossl_sslctx_ex_store_p;
  #endif
  
  static void
  ossl_sslctx_free(void *ptr)
  {
      SSL_CTX *ctx = ptr;
  #if !defined(HAVE_X509_STORE_UP_REF)
      if (ctx && SSL_CTX_get_ex_data(ctx, ossl_sslctx_ex_store_p))
  	ctx->cert_store = NULL;
  #endif
      SSL_CTX_free(ctx);
  }
  
  static const rb_data_type_t ossl_sslctx_type = {
      "OpenSSL/SSL/CTX",
      {
  	0, ossl_sslctx_free,
      },
      0, 0, RUBY_TYPED_FREE_IMMEDIATELY,
  };
  
  static VALUE
  ossl_sslctx_s_alloc(VALUE klass)
  {
      SSL_CTX *ctx;
      long mode = 0 |
  	SSL_MODE_ENABLE_PARTIAL_WRITE |
  	SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER |
  	SSL_MODE_RELEASE_BUFFERS;
      VALUE obj;
  
      obj = TypedData_Wrap_Struct(klass, &ossl_sslctx_type, 0);
  #if OPENSSL_VERSION_NUMBER >= 0x10100000 && !defined(LIBRESSL_VERSION_NUMBER)
      ctx = SSL_CTX_new(TLS_method());
  #else
      ctx = SSL_CTX_new(SSLv23_method());
  #endif
      if (!ctx) {
          ossl_raise(eSSLError, "SSL_CTX_new");
      }
      SSL_CTX_set_mode(ctx, mode);
      RTYPEDDATA_DATA(obj) = ctx;
      SSL_CTX_set_ex_data(ctx, ossl_sslctx_ex_ptr_idx, (void *)obj);
  
  #if !defined(OPENSSL_NO_EC) && defined(HAVE_SSL_CTX_SET_ECDH_AUTO)
      /* We use SSL_CTX_set1_curves_list() to specify the curve used in ECDH. It
       * allows to specify multiple curve names and OpenSSL will select
       * automatically from them. In OpenSSL 1.0.2, the automatic selection has to
       * be enabled explicitly. But OpenSSL 1.1.0 removed the knob and it is
       * always enabled. To uniform the behavior, we enable the automatic
       * selection also in 1.0.2. Users can still disable ECDH by removing ECDH
       * cipher suites by SSLContext#ciphers=. */
      if (!SSL_CTX_set_ecdh_auto(ctx, 1))
  	ossl_raise(eSSLError, "SSL_CTX_set_ecdh_auto");
  #endif
  
      return obj;
  }
  
  static int
  parse_proto_version(VALUE str)
  {
      int i;
      static const struct {
  	const char *name;
  	int version;
      } map[] = {
  	{ "SSL2", SSL2_VERSION },
  	{ "SSL3", SSL3_VERSION },
  	{ "TLS1", TLS1_VERSION },
  	{ "TLS1_1", TLS1_1_VERSION },
  	{ "TLS1_2", TLS1_2_VERSION },
  #ifdef TLS1_3_VERSION
  	{ "TLS1_3", TLS1_3_VERSION },
  #endif
      };
  
      if (NIL_P(str))
  	return 0;
      if (RB_INTEGER_TYPE_P(str))
  	return NUM2INT(str);
  
      if (SYMBOL_P(str))
  	str = rb_sym2str(str);
      StringValue(str);
      for (i = 0; i < numberof(map); i++)
  	if (!strncmp(map[i].name, RSTRING_PTR(str), RSTRING_LEN(str)))
  	    return map[i].version;
      rb_raise(rb_eArgError, "unrecognized version %+"PRIsVALUE, str);
  }
  
  /*
   * call-seq:
   *    ctx.set_minmax_proto_version(min, max) -> nil
   *
   * Sets the minimum and maximum supported protocol versions. See #min_version=
   * and #max_version=.
   */
  static VALUE
  ossl_sslctx_set_minmax_proto_version(VALUE self, VALUE min_v, VALUE max_v)
  {
      SSL_CTX *ctx;
      int min, max;
  
      GetSSLCTX(self, ctx);
      min = parse_proto_version(min_v);
      max = parse_proto_version(max_v);
  
  #ifdef HAVE_SSL_CTX_SET_MIN_PROTO_VERSION
      if (!SSL_CTX_set_min_proto_version(ctx, min))
  	ossl_raise(eSSLError, "SSL_CTX_set_min_proto_version");
      if (!SSL_CTX_set_max_proto_version(ctx, max))
  	ossl_raise(eSSLError, "SSL_CTX_set_max_proto_version");
  #else
      {
  	unsigned long sum = 0, opts = 0;
  	int i;
  	static const struct {
  	    int ver;
  	    unsigned long opts;
  	} options_map[] = {
  	    { SSL2_VERSION, SSL_OP_NO_SSLv2 },
  	    { SSL3_VERSION, SSL_OP_NO_SSLv3 },
  	    { TLS1_VERSION, SSL_OP_NO_TLSv1 },
  	    { TLS1_1_VERSION, SSL_OP_NO_TLSv1_1 },
  	    { TLS1_2_VERSION, SSL_OP_NO_TLSv1_2 },
  # if defined(TLS1_3_VERSION)
  	    { TLS1_3_VERSION, SSL_OP_NO_TLSv1_3 },
  # endif
  	};
  
  	for (i = 0; i < numberof(options_map); i++) {
  	    sum |= options_map[i].opts;
              if ((min && min > options_map[i].ver) ||
                  (max && max < options_map[i].ver)) {
  		opts |= options_map[i].opts;
              }
  	}
  	SSL_CTX_clear_options(ctx, sum);
  	SSL_CTX_set_options(ctx, opts);
      }
  #endif
  
      return Qnil;
  }
  
  static VALUE
  ossl_call_client_cert_cb(VALUE obj)
  {
      VALUE ctx_obj, cb, ary, cert, key;
  
      ctx_obj = rb_attr_get(obj, id_i_context);
      cb = rb_attr_get(ctx_obj, id_i_client_cert_cb);
      if (NIL_P(cb))
  	return Qnil;
  
      ary = rb_funcallv(cb, id_call, 1, &obj);
      Check_Type(ary, T_ARRAY);
      GetX509CertPtr(cert = rb_ary_entry(ary, 0));
      GetPrivPKeyPtr(key = rb_ary_entry(ary, 1));
  
      return rb_ary_new3(2, cert, key);
  }
  
  static int
  ossl_client_cert_cb(SSL *ssl, X509 **x509, EVP_PKEY **pkey)
  {
      VALUE obj, ret;
  
      obj = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
      ret = rb_protect(ossl_call_client_cert_cb, obj, NULL);
      if (NIL_P(ret))
  	return 0;
  
      *x509 = DupX509CertPtr(RARRAY_AREF(ret, 0));
      *pkey = DupPKeyPtr(RARRAY_AREF(ret, 1));
  
      return 1;
  }
  
  #if !defined(OPENSSL_NO_DH)
  struct tmp_dh_callback_args {
      VALUE ssl_obj;
      ID id;
      int type;
      int is_export;
      int keylength;
  };
  
  static EVP_PKEY *
  ossl_call_tmp_dh_callback(struct tmp_dh_callback_args *args)
  {
      VALUE cb, dh;
      EVP_PKEY *pkey;
  
      cb = rb_funcall(args->ssl_obj, args->id, 0);
      if (NIL_P(cb))
  	return NULL;
      dh = rb_funcall(cb, id_call, 3, args->ssl_obj, INT2NUM(args->is_export),
  		    INT2NUM(args->keylength));
      pkey = GetPKeyPtr(dh);
      if (EVP_PKEY_base_id(pkey) != args->type)
  	return NULL;
  
      return pkey;
  }
  #endif
  
  #if !defined(OPENSSL_NO_DH)
  static DH *
  ossl_tmp_dh_callback(SSL *ssl, int is_export, int keylength)
  {
      VALUE rb_ssl;
      EVP_PKEY *pkey;
      struct tmp_dh_callback_args args;
      int state;
  
      rb_ssl = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
      args.ssl_obj = rb_ssl;
      args.id = id_tmp_dh_callback;
      args.is_export = is_export;
      args.keylength = keylength;
      args.type = EVP_PKEY_DH;
  
      pkey = (EVP_PKEY *)rb_protect((VALUE (*)(VALUE))ossl_call_tmp_dh_callback,
  				  (VALUE)&args, &state);
      if (state) {
  	rb_ivar_set(rb_ssl, ID_callback_state, INT2NUM(state));
  	return NULL;
      }
      if (!pkey)
  	return NULL;
  
      return EVP_PKEY_get0_DH(pkey);
  }
  #endif /* OPENSSL_NO_DH */
  
  static VALUE
  call_verify_certificate_identity(VALUE ctx_v)
  {
      X509_STORE_CTX *ctx = (X509_STORE_CTX *)ctx_v;
      SSL *ssl;
      VALUE ssl_obj, hostname, cert_obj;
  
      ssl = X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx());
      ssl_obj = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
      hostname = rb_attr_get(ssl_obj, id_i_hostname);
  
      if (!RTEST(hostname)) {
  	rb_warning("verify_hostname requires hostname to be set");
  	return Qtrue;
      }
  
      cert_obj = ossl_x509_new(X509_STORE_CTX_get_current_cert(ctx));
      return rb_funcall(mSSL, rb_intern("verify_certificate_identity"), 2,
  		      cert_obj, hostname);
  }
  
  static int
  ossl_ssl_verify_callback(int preverify_ok, X509_STORE_CTX *ctx)
  {
      VALUE cb, ssl_obj, sslctx_obj, verify_hostname, ret;
      SSL *ssl;
      int status;
  
      ssl = X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx());
      cb = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_vcb_idx);
      ssl_obj = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
      sslctx_obj = rb_attr_get(ssl_obj, id_i_context);
      verify_hostname = rb_attr_get(sslctx_obj, id_i_verify_hostname);
  
      if (preverify_ok && RTEST(verify_hostname) && !SSL_is_server(ssl) &&
  	!X509_STORE_CTX_get_error_depth(ctx)) {
  	ret = rb_protect(call_verify_certificate_identity, (VALUE)ctx, &status);
  	if (status) {
  	    rb_ivar_set(ssl_obj, ID_callback_state, INT2NUM(status));
  	    return 0;
  	}
          if (ret != Qtrue) {
              preverify_ok = 0;
  #if defined(X509_V_ERR_HOSTNAME_MISMATCH)
              X509_STORE_CTX_set_error(ctx, X509_V_ERR_HOSTNAME_MISMATCH);
  #else
              X509_STORE_CTX_set_error(ctx, X509_V_ERR_CERT_REJECTED);
  #endif
          }
      }
  
      return ossl_verify_cb_call(cb, preverify_ok, ctx);
  }
  
  static VALUE
  ossl_call_session_get_cb(VALUE ary)
  {
      VALUE ssl_obj, cb;
  
      Check_Type(ary, T_ARRAY);
      ssl_obj = rb_ary_entry(ary, 0);
  
      cb = rb_funcall(ssl_obj, rb_intern("session_get_cb"), 0);
      if (NIL_P(cb)) return Qnil;
  
      return rb_funcallv(cb, id_call, 1, &ary);
  }
  
  static SSL_SESSION *
  #if (!defined(LIBRESSL_VERSION_NUMBER) ? OPENSSL_VERSION_NUMBER >= 0x10100000 : LIBRESSL_VERSION_NUMBER >= 0x2080000f)
  ossl_sslctx_session_get_cb(SSL *ssl, const unsigned char *buf, int len, int *copy)
  #else
  ossl_sslctx_session_get_cb(SSL *ssl, unsigned char *buf, int len, int *copy)
  #endif
  {
      VALUE ary, ssl_obj, ret_obj;
      SSL_SESSION *sess;
      int state = 0;
  
      OSSL_Debug("SSL SESSION get callback entered");
      ssl_obj = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
      ary = rb_ary_new2(2);
      rb_ary_push(ary, ssl_obj);
      rb_ary_push(ary, rb_str_new((const char *)buf, len));
  
      ret_obj = rb_protect(ossl_call_session_get_cb, ary, &state);
      if (state) {
          rb_ivar_set(ssl_obj, ID_callback_state, INT2NUM(state));
          return NULL;
      }
      if (!rb_obj_is_instance_of(ret_obj, cSSLSession))
          return NULL;
  
      GetSSLSession(ret_obj, sess);
      *copy = 1;
  
      return sess;
  }
  
  static VALUE
  ossl_call_session_new_cb(VALUE ary)
  {
      VALUE ssl_obj, cb;
  
      Check_Type(ary, T_ARRAY);
      ssl_obj = rb_ary_entry(ary, 0);
  
      cb = rb_funcall(ssl_obj, rb_intern("session_new_cb"), 0);
      if (NIL_P(cb)) return Qnil;
  
      return rb_funcallv(cb, id_call, 1, &ary);
  }
  
  /* return 1 normal.  return 0 removes the session */
  static int
  ossl_sslctx_session_new_cb(SSL *ssl, SSL_SESSION *sess)
  {
      VALUE ary, ssl_obj, sess_obj;
      int state = 0;
  
      OSSL_Debug("SSL SESSION new callback entered");
  
      ssl_obj = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
      sess_obj = rb_obj_alloc(cSSLSession);
      SSL_SESSION_up_ref(sess);
      DATA_PTR(sess_obj) = sess;
  
      ary = rb_ary_new2(2);
      rb_ary_push(ary, ssl_obj);
      rb_ary_push(ary, sess_obj);
  
      rb_protect(ossl_call_session_new_cb, ary, &state);
      if (state) {
          rb_ivar_set(ssl_obj, ID_callback_state, INT2NUM(state));
      }
  
      /*
       * return 0 which means to OpenSSL that the session is still
       * valid (since we created Ruby Session object) and was not freed by us
       * with SSL_SESSION_free(). Call SSLContext#remove_session(sess) in
       * session_get_cb block if you don't want OpenSSL to cache the session
       * internally.
       */
      return 0;
  }
  
  static VALUE
  ossl_call_session_remove_cb(VALUE ary)
  {
      VALUE sslctx_obj, cb;
  
      Check_Type(ary, T_ARRAY);
      sslctx_obj = rb_ary_entry(ary, 0);
  
      cb = rb_attr_get(sslctx_obj, id_i_session_remove_cb);
      if (NIL_P(cb)) return Qnil;
  
      return rb_funcallv(cb, id_call, 1, &ary);
  }
  
  static void
  ossl_sslctx_session_remove_cb(SSL_CTX *ctx, SSL_SESSION *sess)
  {
      VALUE ary, sslctx_obj, sess_obj;
      int state = 0;
  
      /*
       * This callback is also called for all sessions in the internal store
       * when SSL_CTX_free() is called.
       */
      if (rb_during_gc())
  	return;
  
      OSSL_Debug("SSL SESSION remove callback entered");
  
      sslctx_obj = (VALUE)SSL_CTX_get_ex_data(ctx, ossl_sslctx_ex_ptr_idx);
      sess_obj = rb_obj_alloc(cSSLSession);
      SSL_SESSION_up_ref(sess);
      DATA_PTR(sess_obj) = sess;
  
      ary = rb_ary_new2(2);
      rb_ary_push(ary, sslctx_obj);
      rb_ary_push(ary, sess_obj);
  
      rb_protect(ossl_call_session_remove_cb, ary, &state);
      if (state) {
  /*
    the SSL_CTX is frozen, nowhere to save state.
    there is no common accessor method to check it either.
          rb_ivar_set(sslctx_obj, ID_callback_state, INT2NUM(state));
  */
      }
  }
  
  static VALUE
  ossl_sslctx_add_extra_chain_cert_i(RB_BLOCK_CALL_FUNC_ARGLIST(i, arg))
  {
      X509 *x509;
      SSL_CTX *ctx;
  
      GetSSLCTX(arg, ctx);
      x509 = DupX509CertPtr(i);
      if(!SSL_CTX_add_extra_chain_cert(ctx, x509)){
  	ossl_raise(eSSLError, NULL);
      }
  
      return i;
  }
  
  static VALUE ossl_sslctx_setup(VALUE self);
  
  static VALUE
  ossl_call_servername_cb(VALUE ary)
  {
      VALUE ssl_obj, sslctx_obj, cb, ret_obj;
  
      Check_Type(ary, T_ARRAY);
      ssl_obj = rb_ary_entry(ary, 0);
  
      sslctx_obj = rb_attr_get(ssl_obj, id_i_context);
      cb = rb_attr_get(sslctx_obj, id_i_servername_cb);
      if (NIL_P(cb)) return Qnil;
  
      ret_obj = rb_funcallv(cb, id_call, 1, &ary);
      if (rb_obj_is_kind_of(ret_obj, cSSLContext)) {
          SSL *ssl;
          SSL_CTX *ctx2;
  
          ossl_sslctx_setup(ret_obj);
          GetSSL(ssl_obj, ssl);
          GetSSLCTX(ret_obj, ctx2);
          SSL_set_SSL_CTX(ssl, ctx2);
          rb_ivar_set(ssl_obj, id_i_context, ret_obj);
      } else if (!NIL_P(ret_obj)) {
  	ossl_raise(rb_eArgError, "servername_cb must return an "
  		   "OpenSSL::SSL::SSLContext object or nil");
      }
  
      return ret_obj;
  }
  
  static int
  ssl_servername_cb(SSL *ssl, int *ad, void *arg)
  {
      VALUE ary, ssl_obj;
      int state = 0;
      const char *servername = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
  
      if (!servername)
          return SSL_TLSEXT_ERR_OK;
  
      ssl_obj = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
      ary = rb_ary_new2(2);
      rb_ary_push(ary, ssl_obj);
      rb_ary_push(ary, rb_str_new2(servername));
  
      rb_protect(ossl_call_servername_cb, ary, &state);
      if (state) {
          rb_ivar_set(ssl_obj, ID_callback_state, INT2NUM(state));
          return SSL_TLSEXT_ERR_ALERT_FATAL;
      }
  
      return SSL_TLSEXT_ERR_OK;
  }
  
  static void
  ssl_renegotiation_cb(const SSL *ssl)
  {
      VALUE ssl_obj, sslctx_obj, cb;
  
      ssl_obj = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
      sslctx_obj = rb_attr_get(ssl_obj, id_i_context);
      cb = rb_attr_get(sslctx_obj, id_i_renegotiation_cb);
      if (NIL_P(cb)) return;
  
      rb_funcallv(cb, id_call, 1, &ssl_obj);
  }
  
  #if !defined(OPENSSL_NO_NEXTPROTONEG) || \
      defined(HAVE_SSL_CTX_SET_ALPN_SELECT_CB)
  static VALUE
  ssl_npn_encode_protocol_i(RB_BLOCK_CALL_FUNC_ARGLIST(cur, encoded))
  {
      int len = RSTRING_LENINT(cur);
      char len_byte;
      if (len < 1 || len > 255)
  	ossl_raise(eSSLError, "Advertised protocol must have length 1..255");
      /* Encode the length byte */
      len_byte = len;
      rb_str_buf_cat(encoded, &len_byte, 1);
      rb_str_buf_cat(encoded, RSTRING_PTR(cur), len);
      return Qnil;
  }
  
  static VALUE
  ssl_encode_npn_protocols(VALUE protocols)
  {
      VALUE encoded = rb_str_new(NULL, 0);
      rb_iterate(rb_each, protocols, ssl_npn_encode_protocol_i, encoded);
      return encoded;
  }
  
  struct npn_select_cb_common_args {
      VALUE cb;
      const unsigned char *in;
      unsigned inlen;
  };
  
  static VALUE
  npn_select_cb_common_i(VALUE tmp)
  {
      struct npn_select_cb_common_args *args = (void *)tmp;
      const unsigned char *in = args->in, *in_end = in + args->inlen;
      unsigned char l;
      long len;
      VALUE selected, protocols = rb_ary_new();
  
      /* assume OpenSSL verifies this format */
      /* The format is len_1|proto_1|...|len_n|proto_n */
      while (in < in_end) {
  	l = *in++;
  	rb_ary_push(protocols, rb_str_new((const char *)in, l));
  	in += l;
      }
  
      selected = rb_funcallv(args->cb, id_call, 1, &protocols);
      StringValue(selected);
      len = RSTRING_LEN(selected);
      if (len < 1 || len >= 256) {
  	ossl_raise(eSSLError, "Selected protocol name must have length 1..255");
      }
  
      return selected;
  }
  
  static int
  ssl_npn_select_cb_common(SSL *ssl, VALUE cb, const unsigned char **out,
  			 unsigned char *outlen, const unsigned char *in,
  			 unsigned int inlen)
  {
      VALUE selected;
      int status;
      struct npn_select_cb_common_args args;
  
      args.cb = cb;
      args.in = in;
      args.inlen = inlen;
  
      selected = rb_protect(npn_select_cb_common_i, (VALUE)&args, &status);
      if (status) {
  	VALUE ssl_obj = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
  
  	rb_ivar_set(ssl_obj, ID_callback_state, INT2NUM(status));
  	return SSL_TLSEXT_ERR_ALERT_FATAL;
      }
  
      *out = (unsigned char *)RSTRING_PTR(selected);
      *outlen = (unsigned char)RSTRING_LEN(selected);
  
      return SSL_TLSEXT_ERR_OK;
  }
  #endif
  
  #ifndef OPENSSL_NO_NEXTPROTONEG
  static int
  ssl_npn_advertise_cb(SSL *ssl, const unsigned char **out, unsigned int *outlen,
  		     void *arg)
  {
      VALUE protocols = (VALUE)arg;
  
      *out = (const unsigned char *) RSTRING_PTR(protocols);
      *outlen = RSTRING_LENINT(protocols);
  
      return SSL_TLSEXT_ERR_OK;
  }
  
  static int
  ssl_npn_select_cb(SSL *ssl, unsigned char **out, unsigned char *outlen,
  		  const unsigned char *in, unsigned int inlen, void *arg)
  {
      VALUE sslctx_obj, cb;
  
      sslctx_obj = (VALUE) arg;
      cb = rb_attr_get(sslctx_obj, id_i_npn_select_cb);
  
      return ssl_npn_select_cb_common(ssl, cb, (const unsigned char **)out,
  				    outlen, in, inlen);
  }
  #endif
  
  #ifdef HAVE_SSL_CTX_SET_ALPN_SELECT_CB
  static int
  ssl_alpn_select_cb(SSL *ssl, const unsigned char **out, unsigned char *outlen,
  		   const unsigned char *in, unsigned int inlen, void *arg)
  {
      VALUE sslctx_obj, cb;
  
      sslctx_obj = (VALUE) arg;
      cb = rb_attr_get(sslctx_obj, id_i_alpn_select_cb);
  
      return ssl_npn_select_cb_common(ssl, cb, out, outlen, in, inlen);
  }
  #endif
  
  /* This function may serve as the entry point to support further callbacks. */
  static void
  ssl_info_cb(const SSL *ssl, int where, int val)
  {
      int is_server = SSL_is_server((SSL *)ssl);
  
      if (is_server && where & SSL_CB_HANDSHAKE_START) {
  	ssl_renegotiation_cb(ssl);
      }
  }
  
  /*
   * Gets various OpenSSL options.
   */
  static VALUE
  ossl_sslctx_get_options(VALUE self)
  {
      SSL_CTX *ctx;
      GetSSLCTX(self, ctx);
      /*
       * Do explicit cast because SSL_CTX_get_options() returned (signed) long in
       * OpenSSL before 1.1.0.
       */
      return ULONG2NUM((unsigned long)SSL_CTX_get_options(ctx));
  }
  
  /*
   * Sets various OpenSSL options.
   */
  static VALUE
  ossl_sslctx_set_options(VALUE self, VALUE options)
  {
      SSL_CTX *ctx;
  
      rb_check_frozen(self);
      GetSSLCTX(self, ctx);
  
      SSL_CTX_clear_options(ctx, SSL_CTX_get_options(ctx));
  
      if (NIL_P(options)) {
  	SSL_CTX_set_options(ctx, SSL_OP_ALL);
      } else {
  	SSL_CTX_set_options(ctx, NUM2ULONG(options));
      }
  
      return self;
  }
  
  /*
   * call-seq:
   *    ctx.setup => Qtrue # first time
   *    ctx.setup => nil # thereafter
   *
   * This method is called automatically when a new SSLSocket is created.
   * However, it is not thread-safe and must be called before creating
   * SSLSocket objects in a multi-threaded program.
   */
  static VALUE
  ossl_sslctx_setup(VALUE self)
  {
      SSL_CTX *ctx;
      X509 *cert = NULL, *client_ca = NULL;
      EVP_PKEY *key = NULL;
      char *ca_path = NULL, *ca_file = NULL;
      int verify_mode;
      long i;
      VALUE val;
  
      if(OBJ_FROZEN(self)) return Qnil;
      GetSSLCTX(self, ctx);
  
  #if !defined(OPENSSL_NO_DH)
      SSL_CTX_set_tmp_dh_callback(ctx, ossl_tmp_dh_callback);
  #endif
  
  #ifdef HAVE_SSL_CTX_SET_POST_HANDSHAKE_AUTH
      SSL_CTX_set_post_handshake_auth(ctx, 1);
  #endif
  
      val = rb_attr_get(self, id_i_cert_store);
      if (!NIL_P(val)) {
  	X509_STORE *store = GetX509StorePtr(val); /* NO NEED TO DUP */
  	SSL_CTX_set_cert_store(ctx, store);
  #if !defined(HAVE_X509_STORE_UP_REF)
  	/*
           * WORKAROUND:
  	 *   X509_STORE can count references, but
  	 *   X509_STORE_free() doesn't care it.
  	 *   So we won't increment it but mark it by ex_data.
  	 */
          SSL_CTX_set_ex_data(ctx, ossl_sslctx_ex_store_p, ctx);
  #else /* Fixed in OpenSSL 1.0.2; bff9ce4db38b (master), 5b4b9ce976fc (1.0.2) */
  	X509_STORE_up_ref(store);
  #endif
      }
  
      val = rb_attr_get(self, id_i_extra_chain_cert);
      if(!NIL_P(val)){
  	rb_block_call(val, rb_intern("each"), 0, 0, ossl_sslctx_add_extra_chain_cert_i, self);
      }
  
      /* private key may be bundled in certificate file. */
      val = rb_attr_get(self, id_i_cert);
      cert = NIL_P(val) ? NULL : GetX509CertPtr(val); /* NO DUP NEEDED */
      val = rb_attr_get(self, id_i_key);
      key = NIL_P(val) ? NULL : GetPrivPKeyPtr(val); /* NO DUP NEEDED */
      if (cert && key) {
          if (!SSL_CTX_use_certificate(ctx, cert)) {
              /* Adds a ref => Safe to FREE */
              ossl_raise(eSSLError, "SSL_CTX_use_certificate");
          }
          if (!SSL_CTX_use_PrivateKey(ctx, key)) {
              /* Adds a ref => Safe to FREE */
              ossl_raise(eSSLError, "SSL_CTX_use_PrivateKey");
          }
          if (!SSL_CTX_check_private_key(ctx)) {
              ossl_raise(eSSLError, "SSL_CTX_check_private_key");
          }
      }
  
      val = rb_attr_get(self, id_i_client_ca);
      if(!NIL_P(val)){
  	if (RB_TYPE_P(val, T_ARRAY)) {
  	    for(i = 0; i < RARRAY_LEN(val); i++){
  		client_ca = GetX509CertPtr(RARRAY_AREF(val, i));
          	if (!SSL_CTX_add_client_CA(ctx, client_ca)){
  		    /* Copies X509_NAME => FREE it. */
          	    ossl_raise(eSSLError, "SSL_CTX_add_client_CA");
          	}
  	    }
          }
  	else{
  	    client_ca = GetX509CertPtr(val); /* NO DUP NEEDED. */
              if (!SSL_CTX_add_client_CA(ctx, client_ca)){
  		/* Copies X509_NAME => FREE it. */
          	ossl_raise(eSSLError, "SSL_CTX_add_client_CA");
              }
  	}
      }
  
      val = rb_attr_get(self, id_i_ca_file);
      ca_file = NIL_P(val) ? NULL : StringValueCStr(val);
      val = rb_attr_get(self, id_i_ca_path);
      ca_path = NIL_P(val) ? NULL : StringValueCStr(val);
      if(ca_file || ca_path){
  	if (!SSL_CTX_load_verify_locations(ctx, ca_file, ca_path))
  	    rb_warning("can't set verify locations");
      }
  
      val = rb_attr_get(self, id_i_verify_mode);
      verify_mode = NIL_P(val) ? SSL_VERIFY_NONE : NUM2INT(val);
      SSL_CTX_set_verify(ctx, verify_mode, ossl_ssl_verify_callback);
      if (RTEST(rb_attr_get(self, id_i_client_cert_cb)))
  	SSL_CTX_set_client_cert_cb(ctx, ossl_client_cert_cb);
  
      val = rb_attr_get(self, id_i_timeout);
      if(!NIL_P(val)) SSL_CTX_set_timeout(ctx, NUM2LONG(val));
  
      val = rb_attr_get(self, id_i_verify_depth);
      if(!NIL_P(val)) SSL_CTX_set_verify_depth(ctx, NUM2INT(val));
  
  #ifndef OPENSSL_NO_NEXTPROTONEG
      val = rb_attr_get(self, id_i_npn_protocols);
      if (!NIL_P(val)) {
  	VALUE encoded = ssl_encode_npn_protocols(val);
  	rb_ivar_set(self, id_npn_protocols_encoded, encoded);
  	SSL_CTX_set_next_protos_advertised_cb(ctx, ssl_npn_advertise_cb, (void *)encoded);
  	OSSL_Debug("SSL NPN advertise callback added");
      }
      if (RTEST(rb_attr_get(self, id_i_npn_select_cb))) {
  	SSL_CTX_set_next_proto_select_cb(ctx, ssl_npn_select_cb, (void *) self);
  	OSSL_Debug("SSL NPN select callback added");
      }
  #endif
  
  #ifdef HAVE_SSL_CTX_SET_ALPN_SELECT_CB
      val = rb_attr_get(self, id_i_alpn_protocols);
      if (!NIL_P(val)) {
  	VALUE rprotos = ssl_encode_npn_protocols(val);
  
  	/* returns 0 on success */
  	if (SSL_CTX_set_alpn_protos(ctx, (unsigned char *)RSTRING_PTR(rprotos),
  				    RSTRING_LENINT(rprotos)))
  	    ossl_raise(eSSLError, "SSL_CTX_set_alpn_protos");
  	OSSL_Debug("SSL ALPN values added");
      }
      if (RTEST(rb_attr_get(self, id_i_alpn_select_cb))) {
  	SSL_CTX_set_alpn_select_cb(ctx, ssl_alpn_select_cb, (void *) self);
  	OSSL_Debug("SSL ALPN select callback added");
      }
  #endif
  
      rb_obj_freeze(self);
  
      val = rb_attr_get(self, id_i_session_id_context);
      if (!NIL_P(val)){
  	StringValue(val);
  	if (!SSL_CTX_set_session_id_context(ctx, (unsigned char *)RSTRING_PTR(val),
  					    RSTRING_LENINT(val))){
  	    ossl_raise(eSSLError, "SSL_CTX_set_session_id_context");
  	}
      }
  
      if (RTEST(rb_attr_get(self, id_i_session_get_cb))) {
  	SSL_CTX_sess_set_get_cb(ctx, ossl_sslctx_session_get_cb);
  	OSSL_Debug("SSL SESSION get callback added");
      }
      if (RTEST(rb_attr_get(self, id_i_session_new_cb))) {
  	SSL_CTX_sess_set_new_cb(ctx, ossl_sslctx_session_new_cb);
  	OSSL_Debug("SSL SESSION new callback added");
      }
      if (RTEST(rb_attr_get(self, id_i_session_remove_cb))) {
  	SSL_CTX_sess_set_remove_cb(ctx, ossl_sslctx_session_remove_cb);
  	OSSL_Debug("SSL SESSION remove callback added");
      }
  
      val = rb_attr_get(self, id_i_servername_cb);
      if (!NIL_P(val)) {
          SSL_CTX_set_tlsext_servername_callback(ctx, ssl_servername_cb);
  	OSSL_Debug("SSL TLSEXT servername callback added");
      }
  
      return Qtrue;
  }
  
  static VALUE
  ossl_ssl_cipher_to_ary(const SSL_CIPHER *cipher)
  {
      VALUE ary;
      int bits, alg_bits;
  
      ary = rb_ary_new2(4);
      rb_ary_push(ary, rb_str_new2(SSL_CIPHER_get_name(cipher)));
      rb_ary_push(ary, rb_str_new2(SSL_CIPHER_get_version(cipher)));
      bits = SSL_CIPHER_get_bits(cipher, &alg_bits);
      rb_ary_push(ary, INT2NUM(bits));
      rb_ary_push(ary, INT2NUM(alg_bits));
  
      return ary;
  }
  
  /*
   * call-seq:
   *    ctx.ciphers => [[name, version, bits, alg_bits], ...]
   *
   * The list of cipher suites configured for this context.
   */
  static VALUE
  ossl_sslctx_get_ciphers(VALUE self)
  {
      SSL_CTX *ctx;
      STACK_OF(SSL_CIPHER) *ciphers;
      const SSL_CIPHER *cipher;
      VALUE ary;
      int i, num;
  
      GetSSLCTX(self, ctx);
      ciphers = SSL_CTX_get_ciphers(ctx);
      if (!ciphers)
          return rb_ary_new();
  
      num = sk_SSL_CIPHER_num(ciphers);
      ary = rb_ary_new2(num);
      for(i = 0; i < num; i++){
          cipher = sk_SSL_CIPHER_value(ciphers, i);
          rb_ary_push(ary, ossl_ssl_cipher_to_ary(cipher));
      }
      return ary;
  }
  
  /*
   * call-seq:
   *    ctx.ciphers = "cipher1:cipher2:..."
   *    ctx.ciphers = [name, ...]
   *    ctx.ciphers = [[name, version, bits, alg_bits], ...]
   *
   * Sets the list of available cipher suites for this context.  Note in a server
   * context some ciphers require the appropriate certificates.  For example, an
   * RSA cipher suite can only be chosen when an RSA certificate is available.
   */
  static VALUE
  ossl_sslctx_set_ciphers(VALUE self, VALUE v)
  {
      SSL_CTX *ctx;
      VALUE str, elem;
      int i;
  
      rb_check_frozen(self);
      if (NIL_P(v))
  	return v;
      else if (RB_TYPE_P(v, T_ARRAY)) {
          str = rb_str_new(0, 0);
          for (i = 0; i < RARRAY_LEN(v); i++) {
              elem = rb_ary_entry(v, i);
              if (RB_TYPE_P(elem, T_ARRAY)) elem = rb_ary_entry(elem, 0);
              elem = rb_String(elem);
              rb_str_append(str, elem);
              if (i < RARRAY_LEN(v)-1) rb_str_cat2(str, ":");
          }
      } else {
          str = v;
          StringValue(str);
      }
  
      GetSSLCTX(self, ctx);
      if (!SSL_CTX_set_cipher_list(ctx, StringValueCStr(str))) {
          ossl_raise(eSSLError, "SSL_CTX_set_cipher_list");
      }
  
      return v;
  }
  
  #if !defined(OPENSSL_NO_EC)
  /*
   * call-seq:
   *    ctx.ecdh_curves = curve_list -> curve_list
   *
   * Sets the list of "supported elliptic curves" for this context.
   *
   * For a TLS client, the list is directly used in the Supported Elliptic Curves
   * Extension. For a server, the list is used by OpenSSL to determine the set of
   * shared curves. OpenSSL will pick the most appropriate one from it.
   *
   * Note that this works differently with old OpenSSL (<= 1.0.1). Only one curve
   * can be set, and this has no effect for TLS clients.
   *
   * === Example
   *   ctx1 = OpenSSL::SSL::SSLContext.new
   *   ctx1.ecdh_curves = "X25519:P-256:P-224"
   *   svr = OpenSSL::SSL::SSLServer.new(tcp_svr, ctx1)
   *   Thread.new { svr.accept }
   *
   *   ctx2 = OpenSSL::SSL::SSLContext.new
   *   ctx2.ecdh_curves = "P-256"
   *   cli = OpenSSL::SSL::SSLSocket.new(tcp_sock, ctx2)
   *   cli.connect
   *
   *   p cli.tmp_key.group.curve_name
   *   # => "prime256v1" (is an alias for NIST P-256)
   */
  static VALUE
  ossl_sslctx_set_ecdh_curves(VALUE self, VALUE arg)
  {
      SSL_CTX *ctx;
  
      rb_check_frozen(self);
      GetSSLCTX(self, ctx);
      StringValueCStr(arg);
  
  #if defined(HAVE_SSL_CTX_SET1_CURVES_LIST)
      if (!SSL_CTX_set1_curves_list(ctx, RSTRING_PTR(arg)))
  	ossl_raise(eSSLError, NULL);
  #else
      /* OpenSSL does not have SSL_CTX_set1_curves_list()... Fallback to
       * SSL_CTX_set_tmp_ecdh(). So only the first curve is used. */
      {
  	VALUE curve, splitted;
  	EC_KEY *ec;
  	int nid;
  
  	splitted = rb_str_split(arg, ":");
  	if (!RARRAY_LEN(splitted))
  	    ossl_raise(eSSLError, "invalid input format");
  	curve = RARRAY_AREF(splitted, 0);
  	StringValueCStr(curve);
  
  	/* SSL_CTX_set1_curves_list() accepts NIST names */
  	nid = EC_curve_nist2nid(RSTRING_PTR(curve));
  	if (nid == NID_undef)
  	    nid = OBJ_txt2nid(RSTRING_PTR(curve));
  	if (nid == NID_undef)
  	    ossl_raise(eSSLError, "unknown curve name");
  
  	ec = EC_KEY_new_by_curve_name(nid);
  	if (!ec)
  	    ossl_raise(eSSLError, NULL);
  	EC_KEY_set_asn1_flag(ec, OPENSSL_EC_NAMED_CURVE);
  	if (!SSL_CTX_set_tmp_ecdh(ctx, ec)) {
  	    EC_KEY_free(ec);
  	    ossl_raise(eSSLError, "SSL_CTX_set_tmp_ecdh");
  	}
  	EC_KEY_free(ec);
  # if defined(HAVE_SSL_CTX_SET_ECDH_AUTO)
  	/* tmp_ecdh and ecdh_auto conflict. tmp_ecdh is ignored when ecdh_auto
  	 * is enabled. So disable ecdh_auto. */
  	if (!SSL_CTX_set_ecdh_auto(ctx, 0))
  	    ossl_raise(eSSLError, "SSL_CTX_set_ecdh_auto");
  # endif
      }
  #endif
  
      return arg;
  }
  #else
  #define ossl_sslctx_set_ecdh_curves rb_f_notimplement
  #endif
  
  /*
   * call-seq:
   *    ctx.security_level -> Integer
   *
   * Returns the security level for the context.
   *
   * See also OpenSSL::SSL::SSLContext#security_level=.
   */
  static VALUE
  ossl_sslctx_get_security_level(VALUE self)
  {
      SSL_CTX *ctx;
  
      GetSSLCTX(self, ctx);
  
  #if defined(HAVE_SSL_CTX_GET_SECURITY_LEVEL)
      return INT2NUM(SSL_CTX_get_security_level(ctx));
  #else
      (void)ctx;
      return INT2FIX(0);
  #endif
  }
  
  /*
   * call-seq:
   *    ctx.security_level = integer
   *
   * Sets the security level for the context. OpenSSL limits parameters according
   * to the level. The "parameters" include: ciphersuites, curves, key sizes,
   * certificate signature algorithms, protocol version and so on. For example,
   * level 1 rejects parameters offering below 80 bits of security, such as
   * ciphersuites using MD5 for the MAC or RSA keys shorter than 1024 bits.
   *
   * Note that attempts to set such parameters with insufficient security are
   * also blocked. You need to lower the level first.
   *
   * This feature is not supported in OpenSSL < 1.1.0, and setting the level to
   * other than 0 will raise NotImplementedError. Level 0 means everything is
   * permitted, the same behavior as previous versions of OpenSSL.
   *
   * See the manpage of SSL_CTX_set_security_level(3) for details.
   */
  static VALUE
  ossl_sslctx_set_security_level(VALUE self, VALUE value)
  {
      SSL_CTX *ctx;
  
      rb_check_frozen(self);
      GetSSLCTX(self, ctx);
  
  #if defined(HAVE_SSL_CTX_GET_SECURITY_LEVEL)
      SSL_CTX_set_security_level(ctx, NUM2INT(value));
  #else
      (void)ctx;
      if (NUM2INT(value) != 0)
  	ossl_raise(rb_eNotImpError, "setting security level to other than 0 is "
  		   "not supported in this version of OpenSSL");
  #endif
  
      return value;
  }
  
  #ifdef SSL_MODE_SEND_FALLBACK_SCSV
  /*
   * call-seq:
   *    ctx.enable_fallback_scsv() => nil
   *
   * Activate TLS_FALLBACK_SCSV for this context.
   * See RFC 7507.
   */
  static VALUE
  ossl_sslctx_enable_fallback_scsv(VALUE self)
  {
      SSL_CTX *ctx;
  
      GetSSLCTX(self, ctx);
      SSL_CTX_set_mode(ctx, SSL_MODE_SEND_FALLBACK_SCSV);
  
      return Qnil;
  }
  #endif
  
  /*
   * call-seq:
   *    ctx.add_certificate(certiticate, pkey [, extra_certs]) -> self
   *
   * Adds a certificate to the context. _pkey_ must be a corresponding private
   * key with _certificate_.
   *
   * Multiple certificates with different public key type can be added by
   * repeated calls of this method, and OpenSSL will choose the most appropriate
   * certificate during the handshake.
   *
   * #cert=, #key=, and #extra_chain_cert= are old accessor methods for setting
   * certificate and internally call this method.
   *
   * === Parameters
   * _certificate_::
   *   A certificate. An instance of OpenSSL::X509::Certificate.
   * _pkey_::
   *   The private key for _certificate_. An instance of OpenSSL::PKey::PKey.
   * _extra_certs_::
   *   Optional. An array of OpenSSL::X509::Certificate. When sending a
   *   certificate chain, the certificates specified by this are sent following
   *   _certificate_, in the order in the array.
   *
   * === Example
   *   rsa_cert = OpenSSL::X509::Certificate.new(...)
   *   rsa_pkey = OpenSSL::PKey.read(...)
   *   ca_intermediate_cert = OpenSSL::X509::Certificate.new(...)
   *   ctx.add_certificate(rsa_cert, rsa_pkey, [ca_intermediate_cert])
   *
   *   ecdsa_cert = ...
   *   ecdsa_pkey = ...
   *   another_ca_cert = ...
   *   ctx.add_certificate(ecdsa_cert, ecdsa_pkey, [another_ca_cert])
   *
   * === Note
   * OpenSSL before the version 1.0.2 could handle only one extra chain across
   * all key types. Calling this method discards the chain set previously.
   */
  static VALUE
  ossl_sslctx_add_certificate(int argc, VALUE *argv, VALUE self)
  {
      VALUE cert, key, extra_chain_ary;
      SSL_CTX *ctx;
      X509 *x509;
      STACK_OF(X509) *extra_chain = NULL;
      EVP_PKEY *pkey, *pub_pkey;
  
      GetSSLCTX(self, ctx);
      rb_scan_args(argc, argv, "21", &cert, &key, &extra_chain_ary);
      rb_check_frozen(self);
      x509 = GetX509CertPtr(cert);
      pkey = GetPrivPKeyPtr(key);
  
      /*
       * The reference counter is bumped, and decremented immediately.
       * X509_get0_pubkey() is only available in OpenSSL >= 1.1.0.
       */
      pub_pkey = X509_get_pubkey(x509);
      EVP_PKEY_free(pub_pkey);
      if (!pub_pkey)
  	rb_raise(rb_eArgError, "certificate does not contain public key");
      if (EVP_PKEY_cmp(pub_pkey, pkey) != 1)
  	rb_raise(rb_eArgError, "public key mismatch");
  
      if (argc >= 3)
  	extra_chain = ossl_x509_ary2sk(extra_chain_ary);
  
      if (!SSL_CTX_use_certificate(ctx, x509)) {
  	sk_X509_pop_free(extra_chain, X509_free);
  	ossl_raise(eSSLError, "SSL_CTX_use_certificate");
      }
      if (!SSL_CTX_use_PrivateKey(ctx, pkey)) {
  	sk_X509_pop_free(extra_chain, X509_free);
  	ossl_raise(eSSLError, "SSL_CTX_use_PrivateKey");
      }
  
      if (extra_chain) {
  #if OPENSSL_VERSION_NUMBER >= 0x10002000 && !defined(LIBRESSL_VERSION_NUMBER)
  	if (!SSL_CTX_set0_chain(ctx, extra_chain)) {
  	    sk_X509_pop_free(extra_chain, X509_free);
  	    ossl_raise(eSSLError, "SSL_CTX_set0_chain");
  	}
  #else
  	STACK_OF(X509) *orig_extra_chain;
  	X509 *x509_tmp;
  
  	/* First, clear the existing chain */
  	SSL_CTX_get_extra_chain_certs(ctx, &orig_extra_chain);
  	if (orig_extra_chain && sk_X509_num(orig_extra_chain)) {
  	    rb_warning("SSL_CTX_set0_chain() is not available; " \
  		       "clearing previously set certificate chain");
  	    SSL_CTX_clear_extra_chain_certs(ctx);
  	}
  	while ((x509_tmp = sk_X509_shift(extra_chain))) {
  	    /* Transfers ownership */
  	    if (!SSL_CTX_add_extra_chain_cert(ctx, x509_tmp)) {
  		X509_free(x509_tmp);
  		sk_X509_pop_free(extra_chain, X509_free);
  		ossl_raise(eSSLError, "SSL_CTX_add_extra_chain_cert");
  	    }
  	}
  	sk_X509_free(extra_chain);
  #endif
      }
      return self;
  }
  
  /*
   *  call-seq:
   *     ctx.session_add(session) -> true | false
   *
   * Adds _session_ to the session cache.
   */
  static VALUE
  ossl_sslctx_session_add(VALUE self, VALUE arg)
  {
      SSL_CTX *ctx;
      SSL_SESSION *sess;
  
      GetSSLCTX(self, ctx);
      GetSSLSession(arg, sess);
  
      return SSL_CTX_add_session(ctx, sess) == 1 ? Qtrue : Qfalse;
  }
  
  /*
   *  call-seq:
   *     ctx.session_remove(session) -> true | false
   *
   * Removes _session_ from the session cache.
   */
  static VALUE
  ossl_sslctx_session_remove(VALUE self, VALUE arg)
  {
      SSL_CTX *ctx;
      SSL_SESSION *sess;
  
      GetSSLCTX(self, ctx);
      GetSSLSession(arg, sess);
  
      return SSL_CTX_remove_session(ctx, sess) == 1 ? Qtrue : Qfalse;
  }
  
  /*
   *  call-seq:
   *     ctx.session_cache_mode -> Integer
   *
   * The current session cache mode.
   */
  static VALUE
  ossl_sslctx_get_session_cache_mode(VALUE self)
  {
      SSL_CTX *ctx;
  
      GetSSLCTX(self, ctx);
  
      return LONG2NUM(SSL_CTX_get_session_cache_mode(ctx));
  }
  
  /*
   *  call-seq:
   *     ctx.session_cache_mode=(integer) -> Integer
   *
   * Sets the SSL session cache mode.  Bitwise-or together the desired
   * SESSION_CACHE_* constants to set.  See SSL_CTX_set_session_cache_mode(3) for
   * details.
   */
  static VALUE
  ossl_sslctx_set_session_cache_mode(VALUE self, VALUE arg)
  {
      SSL_CTX *ctx;
  
      GetSSLCTX(self, ctx);
  
      SSL_CTX_set_session_cache_mode(ctx, NUM2LONG(arg));
  
      return arg;
  }
  
  /*
   *  call-seq:
   *     ctx.session_cache_size -> Integer
   *
   * Returns the current session cache size.  Zero is used to represent an
   * unlimited cache size.
   */
  static VALUE
  ossl_sslctx_get_session_cache_size(VALUE self)
  {
      SSL_CTX *ctx;
  
      GetSSLCTX(self, ctx);
  
      return LONG2NUM(SSL_CTX_sess_get_cache_size(ctx));
  }
  
  /*
   *  call-seq:
   *     ctx.session_cache_size=(integer) -> Integer
   *
   * Sets the session cache size.  Returns the previously valid session cache
   * size.  Zero is used to represent an unlimited session cache size.
   */
  static VALUE
  ossl_sslctx_set_session_cache_size(VALUE self, VALUE arg)
  {
      SSL_CTX *ctx;
  
      GetSSLCTX(self, ctx);
  
      SSL_CTX_sess_set_cache_size(ctx, NUM2LONG(arg));
  
      return arg;
  }
  
  /*
   *  call-seq:
   *     ctx.session_cache_stats -> Hash
   *
   * Returns a Hash containing the following keys:
   *
   * :accept:: Number of started SSL/TLS handshakes in server mode
   * :accept_good:: Number of established SSL/TLS sessions in server mode
   * :accept_renegotiate:: Number of start renegotiations in server mode
   * :cache_full:: Number of sessions that were removed due to cache overflow
   * :cache_hits:: Number of successfully reused connections
   * :cache_misses:: Number of sessions proposed by clients that were not found
   *                 in the cache
   * :cache_num:: Number of sessions in the internal session cache
   * :cb_hits:: Number of sessions retrieved from the external cache in server
   *            mode
   * :connect:: Number of started SSL/TLS handshakes in client mode
   * :connect_good:: Number of established SSL/TLS sessions in client mode
   * :connect_renegotiate:: Number of start renegotiations in client mode
   * :timeouts:: Number of sessions proposed by clients that were found in the
   *             cache but had expired due to timeouts
   */
  static VALUE
  ossl_sslctx_get_session_cache_stats(VALUE self)
  {
      SSL_CTX *ctx;
      VALUE hash;
  
      GetSSLCTX(self, ctx);
  
      hash = rb_hash_new();
      rb_hash_aset(hash, ID2SYM(rb_intern("cache_num")), LONG2NUM(SSL_CTX_sess_number(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("connect")), LONG2NUM(SSL_CTX_sess_connect(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("connect_good")), LONG2NUM(SSL_CTX_sess_connect_good(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("connect_renegotiate")), LONG2NUM(SSL_CTX_sess_connect_renegotiate(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("accept")), LONG2NUM(SSL_CTX_sess_accept(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("accept_good")), LONG2NUM(SSL_CTX_sess_accept_good(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("accept_renegotiate")), LONG2NUM(SSL_CTX_sess_accept_renegotiate(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("cache_hits")), LONG2NUM(SSL_CTX_sess_hits(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("cb_hits")), LONG2NUM(SSL_CTX_sess_cb_hits(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("cache_misses")), LONG2NUM(SSL_CTX_sess_misses(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("cache_full")), LONG2NUM(SSL_CTX_sess_cache_full(ctx)));
      rb_hash_aset(hash, ID2SYM(rb_intern("timeouts")), LONG2NUM(SSL_CTX_sess_timeouts(ctx)));
  
      return hash;
  }
  
  
  /*
   *  call-seq:
   *     ctx.flush_sessions(time) -> self
   *
   * Removes sessions in the internal cache that have expired at _time_.
   */
  static VALUE
  ossl_sslctx_flush_sessions(int argc, VALUE *argv, VALUE self)
  {
      VALUE arg1;
      SSL_CTX *ctx;
      time_t tm = 0;
  
      rb_scan_args(argc, argv, "01", &arg1);
  
      GetSSLCTX(self, ctx);
  
      if (NIL_P(arg1)) {
          tm = time(0);
      } else if (rb_obj_is_instance_of(arg1, rb_cTime)) {
          tm = NUM2LONG(rb_funcall(arg1, rb_intern("to_i"), 0));
      } else {
          ossl_raise(rb_eArgError, "arg must be Time or nil");
      }
  
      SSL_CTX_flush_sessions(ctx, (long)tm);
  
      return self;
  }
  
  /*
   * SSLSocket class
   */
  #ifndef OPENSSL_NO_SOCK
  static inline int
  ssl_started(SSL *ssl)
  {
      /* the FD is set in ossl_ssl_setup(), called by #connect or #accept */
      return SSL_get_fd(ssl) >= 0;
  }
  
  static void
  ossl_ssl_free(void *ssl)
  {
      SSL_free(ssl);
  }
  
  const rb_data_type_t ossl_ssl_type = {
      "OpenSSL/SSL",
      {
  	0, ossl_ssl_free,
      },
      0, 0, RUBY_TYPED_FREE_IMMEDIATELY,
  };
  
  static VALUE
  ossl_ssl_s_alloc(VALUE klass)
  {
      return TypedData_Wrap_Struct(klass, &ossl_ssl_type, NULL);
  }
  
  /*
   * call-seq:
   *    SSLSocket.new(io) => aSSLSocket
   *    SSLSocket.new(io, ctx) => aSSLSocket
   *
   * Creates a new SSL socket from _io_ which must be a real IO object (not an
   * IO-like object that responds to read/write).
   *
   * If _ctx_ is provided the SSL Sockets initial params will be taken from
   * the context.
   *
   * The OpenSSL::Buffering module provides additional IO methods.
   *
   * This method will freeze the SSLContext if one is provided;
   * however, session management is still allowed in the frozen SSLContext.
   */
  static VALUE
  ossl_ssl_initialize(int argc, VALUE *argv, VALUE self)
  {
      VALUE io, v_ctx, verify_cb;
      SSL *ssl;
      SSL_CTX *ctx;
  
      TypedData_Get_Struct(self, SSL, &ossl_ssl_type, ssl);
      if (ssl)
  	ossl_raise(eSSLError, "SSL already initialized");
  
      if (rb_scan_args(argc, argv, "11", &io, &v_ctx) == 1)
  	v_ctx = rb_funcall(cSSLContext, rb_intern("new"), 0);
  
      GetSSLCTX(v_ctx, ctx);
      rb_ivar_set(self, id_i_context, v_ctx);
      ossl_sslctx_setup(v_ctx);
  
      if (rb_respond_to(io, rb_intern("nonblock=")))
  	rb_funcall(io, rb_intern("nonblock="), 1, Qtrue);
      rb_ivar_set(self, id_i_io, io);
  
      ssl = SSL_new(ctx);
      if (!ssl)
  	ossl_raise(eSSLError, NULL);
      RTYPEDDATA_DATA(self) = ssl;
  
      SSL_set_ex_data(ssl, ossl_ssl_ex_ptr_idx, (void *)self);
      SSL_set_info_callback(ssl, ssl_info_cb);
      verify_cb = rb_attr_get(v_ctx, id_i_verify_callback);
      SSL_set_ex_data(ssl, ossl_ssl_ex_vcb_idx, (void *)verify_cb);
  
      rb_call_super(0, NULL);
  
      return self;
  }
  
  static VALUE
  ossl_ssl_setup(VALUE self)
  {
      VALUE io;
      SSL *ssl;
      rb_io_t *fptr;
  
      GetSSL(self, ssl);
      if (ssl_started(ssl))
  	return Qtrue;
  
      io = rb_attr_get(self, id_i_io);
      GetOpenFile(io, fptr);
      rb_io_check_readable(fptr);
      rb_io_check_writable(fptr);
      if (!SSL_set_fd(ssl, TO_SOCKET(fptr->fd)))
  	ossl_raise(eSSLError, "SSL_set_fd");
  
      return Qtrue;
  }
  
  #ifdef _WIN32
  #define ssl_get_error(ssl, ret) (errno = rb_w32_map_errno(WSAGetLastError()), SSL_get_error((ssl), (ret)))
  #else
  #define ssl_get_error(ssl, ret) SSL_get_error((ssl), (ret))
  #endif
  
  static void
  write_would_block(int nonblock)
  {
      if (nonblock)
  	ossl_raise(eSSLErrorWaitWritable, "write would block");
  }
  
  static void
  read_would_block(int nonblock)
  {
      if (nonblock)
  	ossl_raise(eSSLErrorWaitReadable, "read would block");
  }
  
  static int
  no_exception_p(VALUE opts)
  {
      if (RB_TYPE_P(opts, T_HASH) &&
            rb_hash_lookup2(opts, sym_exception, Qundef) == Qfalse)
  	return 1;
      return 0;
  }
  
  static VALUE
  ossl_start_ssl(VALUE self, int (*func)(), const char *funcname, VALUE opts)
  {
      SSL *ssl;
      rb_io_t *fptr;
      int ret, ret2;
      VALUE cb_state;
      int nonblock = opts != Qfalse;
  #if defined(SSL_R_CERTIFICATE_VERIFY_FAILED)
      unsigned long err;
  #endif
  
      rb_ivar_set(self, ID_callback_state, Qnil);
  
      GetSSL(self, ssl);
  
      GetOpenFile(rb_attr_get(self, id_i_io), fptr);
      for(;;){
  	ret = func(ssl);
  
  	cb_state = rb_attr_get(self, ID_callback_state);
          if (!NIL_P(cb_state)) {
  	    /* must cleanup OpenSSL error stack before re-raising */
  	    ossl_clear_error();
  	    rb_jump_tag(NUM2INT(cb_state));
  	}
  
  	if (ret > 0)
  	    break;
  
  	switch((ret2 = ssl_get_error(ssl, ret))){
  	case SSL_ERROR_WANT_WRITE:
              if (no_exception_p(opts)) { return sym_wait_writable; }
              write_would_block(nonblock);
              rb_io_wait_writable(fptr->fd);
              continue;
  	case SSL_ERROR_WANT_READ:
              if (no_exception_p(opts)) { return sym_wait_readable; }
              read_would_block(nonblock);
              rb_io_wait_readable(fptr->fd);
              continue;
  	case SSL_ERROR_SYSCALL:
  	    if (errno) rb_sys_fail(funcname);
  	    ossl_raise(eSSLError, "%s SYSCALL returned=%d errno=%d state=%s", funcname, ret2, errno, SSL_state_string_long(ssl));
  #if defined(SSL_R_CERTIFICATE_VERIFY_FAILED)
  	case SSL_ERROR_SSL:
  	    err = ERR_peek_last_error();
  	    if (ERR_GET_LIB(err) == ERR_LIB_SSL &&
  		ERR_GET_REASON(err) == SSL_R_CERTIFICATE_VERIFY_FAILED) {
  		const char *err_msg = ERR_reason_error_string(err),
  		      *verify_msg = X509_verify_cert_error_string(SSL_get_verify_result(ssl));
  		if (!err_msg)
  		    err_msg = "(null)";
  		if (!verify_msg)
  		    verify_msg = "(null)";
  		ossl_clear_error(); /* let ossl_raise() not append message */
  		ossl_raise(eSSLError, "%s returned=%d errno=%d state=%s: %s (%s)",
  			   funcname, ret2, errno, SSL_state_string_long(ssl),
  			   err_msg, verify_msg);
  	    }
  #endif
  	default:
  	    ossl_raise(eSSLError, "%s returned=%d errno=%d state=%s", funcname, ret2, errno, SSL_state_string_long(ssl));
  	}
      }
  
      return self;
  }
  
  /*
   * call-seq:
   *    ssl.connect => self
   *
   * Initiates an SSL/TLS handshake with a server.  The handshake may be started
   * after unencrypted data has been sent over the socket.
   */
  static VALUE
  ossl_ssl_connect(VALUE self)
  {
      ossl_ssl_setup(self);
  
      return ossl_start_ssl(self, SSL_connect, "SSL_connect", Qfalse);
  }
  
  /*
   * call-seq:
   *    ssl.connect_nonblock([options]) => self
   *
   * Initiates the SSL/TLS handshake as a client in non-blocking manner.
   *
   *   # emulates blocking connect
   *   begin
   *     ssl.connect_nonblock
   *   rescue IO::WaitReadable
   *     IO.select([s2])
   *     retry
   *   rescue IO::WaitWritable
   *     IO.select(nil, [s2])
   *     retry
   *   end
   *
   * By specifying a keyword argument _exception_ to +false+, you can indicate
   * that connect_nonblock should not raise an IO::WaitReadable or
   * IO::WaitWritable exception, but return the symbol +:wait_readable+ or
   * +:wait_writable+ instead.
   */
  static VALUE
  ossl_ssl_connect_nonblock(int argc, VALUE *argv, VALUE self)
  {
      VALUE opts;
      rb_scan_args(argc, argv, "0:", &opts);
  
      ossl_ssl_setup(self);
  
      return ossl_start_ssl(self, SSL_connect, "SSL_connect", opts);
  }
  
  /*
   * call-seq:
   *    ssl.accept => self
   *
   * Waits for a SSL/TLS client to initiate a handshake.  The handshake may be
   * started after unencrypted data has been sent over the socket.
   */
  static VALUE
  ossl_ssl_accept(VALUE self)
  {
      ossl_ssl_setup(self);
  
      return ossl_start_ssl(self, SSL_accept, "SSL_accept", Qfalse);
  }
  
  /*
   * call-seq:
   *    ssl.accept_nonblock([options]) => self
   *
   * Initiates the SSL/TLS handshake as a server in non-blocking manner.
   *
   *   # emulates blocking accept
   *   begin
   *     ssl.accept_nonblock
   *   rescue IO::WaitReadable
   *     IO.select([s2])
   *     retry
   *   rescue IO::WaitWritable
   *     IO.select(nil, [s2])
   *     retry
   *   end
   *
   * By specifying a keyword argument _exception_ to +false+, you can indicate
   * that accept_nonblock should not raise an IO::WaitReadable or
   * IO::WaitWritable exception, but return the symbol +:wait_readable+ or
   * +:wait_writable+ instead.
   */
  static VALUE
  ossl_ssl_accept_nonblock(int argc, VALUE *argv, VALUE self)
  {
      VALUE opts;
  
      rb_scan_args(argc, argv, "0:", &opts);
      ossl_ssl_setup(self);
  
      return ossl_start_ssl(self, SSL_accept, "SSL_accept", opts);
  }
  
  static VALUE
  ossl_ssl_read_internal(int argc, VALUE *argv, VALUE self, int nonblock)
  {
      SSL *ssl;
      int ilen, nread = 0;
      VALUE len, str;
      rb_io_t *fptr;
      VALUE io, opts = Qnil;
  
      if (nonblock) {
  	rb_scan_args(argc, argv, "11:", &len, &str, &opts);
      } else {
  	rb_scan_args(argc, argv, "11", &len, &str);
      }
  
      ilen = NUM2INT(len);
      if (NIL_P(str))
  	str = rb_str_new(0, ilen);
      else {
  	StringValue(str);
  	if (RSTRING_LEN(str) >= ilen)
  	    rb_str_modify(str);
  	else
  	    rb_str_modify_expand(str, ilen - RSTRING_LEN(str));
      }
      rb_str_set_len(str, 0);
      if (ilen == 0)
  	return str;
  
      GetSSL(self, ssl);
      io = rb_attr_get(self, id_i_io);
      GetOpenFile(io, fptr);
      if (ssl_started(ssl)) {
  	for (;;){
  	    nread = SSL_read(ssl, RSTRING_PTR(str), ilen);
  	    switch(ssl_get_error(ssl, nread)){
  	    case SSL_ERROR_NONE:
  		goto end;
  	    case SSL_ERROR_ZERO_RETURN:
  		if (no_exception_p(opts)) { return Qnil; }
  		rb_eof_error();
  	    case SSL_ERROR_WANT_WRITE:
  		if (no_exception_p(opts)) { return sym_wait_writable; }
                  write_would_block(nonblock);
                  rb_io_wait_writable(fptr->fd);
                  continue;
  	    case SSL_ERROR_WANT_READ:
  		if (no_exception_p(opts)) { return sym_wait_readable; }
                  read_would_block(nonblock);
                  rb_io_wait_readable(fptr->fd);
  		continue;
  	    case SSL_ERROR_SYSCALL:
  		if (!ERR_peek_error()) {
  		    if (errno)
  			rb_sys_fail(0);
  		    else {
  			/*
  			 * The underlying BIO returned 0. This is actually a
  			 * protocol error. But unfortunately, not all
  			 * implementations cleanly shutdown the TLS connection
  			 * but just shutdown/close the TCP connection. So report
  			 * EOF for now...
  			 */
  			if (no_exception_p(opts)) { return Qnil; }
  			rb_eof_error();
  		    }
  		}
                  /* fall through */
  	    default:
  		ossl_raise(eSSLError, "SSL_read");
  	    }
          }
      }
      else {
          ID meth = nonblock ? rb_intern("read_nonblock") : rb_intern("sysread");
  
          rb_warning("SSL session is not started yet.");
  #if defined(RB_PASS_KEYWORDS)
          if (nonblock) {
              VALUE argv[3];
              argv[0] = len;
              argv[1] = str;
              argv[2] = opts;
              return rb_funcallv_kw(io, meth, 3, argv, RB_PASS_KEYWORDS);
          }
  #else
          if (nonblock) {
              return rb_funcall(io, meth, 3, len, str, opts);
          }
  #endif
          else
              return rb_funcall(io, meth, 2, len, str);
      }
  
    end:
      rb_str_set_len(str, nread);
      return str;
  }
  
  /*
   * call-seq:
   *    ssl.sysread(length) => string
   *    ssl.sysread(length, buffer) => buffer
   *
   * Reads _length_ bytes from the SSL connection.  If a pre-allocated _buffer_
   * is provided the data will be written into it.
   */
  static VALUE
  ossl_ssl_read(int argc, VALUE *argv, VALUE self)
  {
      return ossl_ssl_read_internal(argc, argv, self, 0);
  }
  
  /*
   * call-seq:
   *    ssl.sysread_nonblock(length) => string
   *    ssl.sysread_nonblock(length, buffer) => buffer
   *    ssl.sysread_nonblock(length[, buffer [, opts]) => buffer
   *
   * A non-blocking version of #sysread.  Raises an SSLError if reading would
   * block.  If "exception: false" is passed, this method returns a symbol of
   * :wait_readable, :wait_writable, or nil, rather than raising an exception.
   *
   * Reads _length_ bytes from the SSL connection.  If a pre-allocated _buffer_
   * is provided the data will be written into it.
   */
  static VALUE
  ossl_ssl_read_nonblock(int argc, VALUE *argv, VALUE self)
  {
      return ossl_ssl_read_internal(argc, argv, self, 1);
  }
  
  static VALUE
  ossl_ssl_write_internal(VALUE self, VALUE str, VALUE opts)
  {
      SSL *ssl;
      int nwrite = 0;
      rb_io_t *fptr;
      int nonblock = opts != Qfalse;
      VALUE io;
  
      StringValue(str);
      GetSSL(self, ssl);
      io = rb_attr_get(self, id_i_io);
      GetOpenFile(io, fptr);
      if (ssl_started(ssl)) {
  	for (;;){
  	    int num = RSTRING_LENINT(str);
  
  	    /* SSL_write(3ssl) manpage states num == 0 is undefined */
  	    if (num == 0)
  		goto end;
  
  	    nwrite = SSL_write(ssl, RSTRING_PTR(str), num);
  	    switch(ssl_get_error(ssl, nwrite)){
  	    case SSL_ERROR_NONE:
  		goto end;
  	    case SSL_ERROR_WANT_WRITE:
  		if (no_exception_p(opts)) { return sym_wait_writable; }
                  write_would_block(nonblock);
                  rb_io_wait_writable(fptr->fd);
                  continue;
  	    case SSL_ERROR_WANT_READ:
  		if (no_exception_p(opts)) { return sym_wait_readable; }
                  read_would_block(nonblock);
                  rb_io_wait_readable(fptr->fd);
                  continue;
  	    case SSL_ERROR_SYSCALL:
  		if (errno) rb_sys_fail(0);
  	    default:
  		ossl_raise(eSSLError, "SSL_write");
  	    }
          }
      }
      else {
  	ID meth = nonblock ?
  	    rb_intern("write_nonblock") : rb_intern("syswrite");
  
          rb_warning("SSL session is not started yet.");
  #if defined(RB_PASS_KEYWORDS)
          if (nonblock) {
              VALUE argv[2];
              argv[0] = str;
              argv[1] = opts;
              return rb_funcallv_kw(io, meth, 2, argv, RB_PASS_KEYWORDS);
          }
  #else
          if (nonblock) {
              return rb_funcall(io, meth, 2, str, opts);
          }
  #endif
          else
              return rb_funcall(io, meth, 1, str);
      }
  
    end:
      return INT2NUM(nwrite);
  }
  
  /*
   * call-seq:
   *    ssl.syswrite(string) => Integer
   *
   * Writes _string_ to the SSL connection.
   */
  static VALUE
  ossl_ssl_write(VALUE self, VALUE str)
  {
      return ossl_ssl_write_internal(self, str, Qfalse);
  }
  
  /*
   * call-seq:
   *    ssl.syswrite_nonblock(string) => Integer
   *
   * Writes _string_ to the SSL connection in a non-blocking manner.  Raises an
   * SSLError if writing would block.
   */
  static VALUE
  ossl_ssl_write_nonblock(int argc, VALUE *argv, VALUE self)
  {
      VALUE str, opts;
  
      rb_scan_args(argc, argv, "1:", &str, &opts);
  
      return ossl_ssl_write_internal(self, str, opts);
  }
  
  /*
   * call-seq:
   *    ssl.stop => nil
   *
   * Sends "close notify" to the peer and tries to shut down the SSL connection
   * gracefully.
   */
  static VALUE
  ossl_ssl_stop(VALUE self)
  {
      SSL *ssl;
      int ret;
  
      GetSSL(self, ssl);
      if (!ssl_started(ssl))
  	return Qnil;
      ret = SSL_shutdown(ssl);
      if (ret == 1) /* Have already received close_notify */
  	return Qnil;
      if (ret == 0) /* Sent close_notify, but we don't wait for reply */
  	return Qnil;
  
      /*
       * XXX: Something happened. Possibly it failed because the underlying socket
       * is not writable/readable, since it is in non-blocking mode. We should do
       * some proper error handling using SSL_get_error() and maybe retry, but we
       * can't block here. Give up for now.
       */
      ossl_clear_error();
      return Qnil;
  }
  
  /*
   * call-seq:
   *    ssl.cert => cert or nil
   *
   * The X509 certificate for this socket endpoint.
   */
  static VALUE
  ossl_ssl_get_cert(VALUE self)
  {
      SSL *ssl;
      X509 *cert = NULL;
  
      GetSSL(self, ssl);
  
      /*
       * Is this OpenSSL bug? Should add a ref?
       * TODO: Ask for.
       */
      cert = SSL_get_certificate(ssl); /* NO DUPs => DON'T FREE. */
  
      if (!cert) {
          return Qnil;
      }
      return ossl_x509_new(cert);
  }
  
  /*
   * call-seq:
   *    ssl.peer_cert => cert or nil
   *
   * The X509 certificate for this socket's peer.
   */
  static VALUE
  ossl_ssl_get_peer_cert(VALUE self)
  {
      SSL *ssl;
      X509 *cert = NULL;
      VALUE obj;
  
      GetSSL(self, ssl);
  
      cert = SSL_get_peer_certificate(ssl); /* Adds a ref => Safe to FREE. */
  
      if (!cert) {
          return Qnil;
      }
      obj = ossl_x509_new(cert);
      X509_free(cert);
  
      return obj;
  }
  
  /*
   * call-seq:
   *    ssl.peer_cert_chain => [cert, ...] or nil
   *
   * The X509 certificate chain for this socket's peer.
   */
  static VALUE
  ossl_ssl_get_peer_cert_chain(VALUE self)
  {
      SSL *ssl;
      STACK_OF(X509) *chain;
      X509 *cert;
      VALUE ary;
      int i, num;
  
      GetSSL(self, ssl);
  
      chain = SSL_get_peer_cert_chain(ssl);
      if(!chain) return Qnil;
      num = sk_X509_num(chain);
      ary = rb_ary_new2(num);
      for (i = 0; i < num; i++){
  	cert = sk_X509_value(chain, i);
  	rb_ary_push(ary, ossl_x509_new(cert));
      }
  
      return ary;
  }
  
  /*
  * call-seq:
  *    ssl.ssl_version => String
  *
  * Returns a String representing the SSL/TLS version that was negotiated
  * for the connection, for example "TLSv1.2".
  */
  static VALUE
  ossl_ssl_get_version(VALUE self)
  {
      SSL *ssl;
  
      GetSSL(self, ssl);
  
      return rb_str_new2(SSL_get_version(ssl));
  }
  
  /*
   * call-seq:
   *    ssl.cipher -> nil or [name, version, bits, alg_bits]
   *
   * Returns the cipher suite actually used in the current session, or nil if
   * no session has been established.
   */
  static VALUE
  ossl_ssl_get_cipher(VALUE self)
  {
      SSL *ssl;
      const SSL_CIPHER *cipher;
  
      GetSSL(self, ssl);
      cipher = SSL_get_current_cipher(ssl);
      return cipher ? ossl_ssl_cipher_to_ary(cipher) : Qnil;
  }
  
  /*
   * call-seq:
   *    ssl.state => string
   *
   * A description of the current connection state. This is for diagnostic
   * purposes only.
   */
  static VALUE
  ossl_ssl_get_state(VALUE self)
  {
      SSL *ssl;
      VALUE ret;
  
      GetSSL(self, ssl);
  
      ret = rb_str_new2(SSL_state_string(ssl));
      if (ruby_verbose) {
          rb_str_cat2(ret, ": ");
          rb_str_cat2(ret, SSL_state_string_long(ssl));
      }
      return ret;
  }
  
  /*
   * call-seq:
   *    ssl.pending => Integer
   *
   * The number of bytes that are immediately available for reading.
   */
  static VALUE
  ossl_ssl_pending(VALUE self)
  {
      SSL *ssl;
  
      GetSSL(self, ssl);
  
      return INT2NUM(SSL_pending(ssl));
  }
  
  /*
   * call-seq:
   *    ssl.session_reused? -> true | false
   *
   * Returns +true+ if a reused session was negotiated during the handshake.
   */
  static VALUE
  ossl_ssl_session_reused(VALUE self)
  {
      SSL *ssl;
  
      GetSSL(self, ssl);
  
      return SSL_session_reused(ssl) ? Qtrue : Qfalse;
  }
  
  /*
   * call-seq:
   *    ssl.session = session -> session
   *
   * Sets the Session to be used when the connection is established.
   */
  static VALUE
  ossl_ssl_set_session(VALUE self, VALUE arg1)
  {
      SSL *ssl;
      SSL_SESSION *sess;
  
      GetSSL(self, ssl);
      GetSSLSession(arg1, sess);
  
      if (SSL_set_session(ssl, sess) != 1)
          ossl_raise(eSSLError, "SSL_set_session");
  
      return arg1;
  }
  
  /*
   * call-seq:
   *    ssl.hostname = hostname -> hostname
   *
   * Sets the server hostname used for SNI. This needs to be set before
   * SSLSocket#connect.
   */
  static VALUE
  ossl_ssl_set_hostname(VALUE self, VALUE arg)
  {
      SSL *ssl;
      char *hostname = NULL;
  
      GetSSL(self, ssl);
  
      if (!NIL_P(arg))
  	hostname = StringValueCStr(arg);
  
      if (!SSL_set_tlsext_host_name(ssl, hostname))
  	ossl_raise(eSSLError, NULL);
  
      /* for SSLSocket#hostname */
      rb_ivar_set(self, id_i_hostname, arg);
  
      return arg;
  }
  
  /*
   * call-seq:
   *    ssl.verify_result => Integer
   *
   * Returns the result of the peer certificates verification.  See verify(1)
   * for error values and descriptions.
   *
   * If no peer certificate was presented X509_V_OK is returned.
   */
  static VALUE
  ossl_ssl_get_verify_result(VALUE self)
  {
      SSL *ssl;
  
      GetSSL(self, ssl);
  
      return LONG2NUM(SSL_get_verify_result(ssl));
  }
  
  /*
   * call-seq:
   *    ssl.finished_message => "finished message"
   *
   * Returns the last *Finished* message sent
   *
   */
  static VALUE
  ossl_ssl_get_finished(VALUE self)
  {
      SSL *ssl;
      char sizer[1], *buf;
      size_t len;
  
      GetSSL(self, ssl);
  
      len = SSL_get_finished(ssl, sizer, 0);
      if (len == 0)
          return Qnil;
  
      buf = ALLOCA_N(char, len);
      SSL_get_finished(ssl, buf, len);
      return rb_str_new(buf, len);
  }
  
  /*
   * call-seq:
   *    ssl.peer_finished_message => "peer finished message"
   *
   * Returns the last *Finished* message received
   *
   */
  static VALUE
  ossl_ssl_get_peer_finished(VALUE self)
  {
      SSL *ssl;
      char sizer[1], *buf;
      size_t len;
  
      GetSSL(self, ssl);
  
      len = SSL_get_peer_finished(ssl, sizer, 0);
      if (len == 0)
          return Qnil;
  
      buf = ALLOCA_N(char, len);
      SSL_get_peer_finished(ssl, buf, len);
      return rb_str_new(buf, len);
  }
  
  /*
   * call-seq:
   *    ssl.client_ca => [x509name, ...]
   *
   * Returns the list of client CAs. Please note that in contrast to
   * SSLContext#client_ca= no array of X509::Certificate is returned but
   * X509::Name instances of the CA's subject distinguished name.
   *
   * In server mode, returns the list set by SSLContext#client_ca=.
   * In client mode, returns the list of client CAs sent from the server.
   */
  static VALUE
  ossl_ssl_get_client_ca_list(VALUE self)
  {
      SSL *ssl;
      STACK_OF(X509_NAME) *ca;
  
      GetSSL(self, ssl);
  
      ca = SSL_get_client_CA_list(ssl);
      return ossl_x509name_sk2ary(ca);
  }
  
  # ifndef OPENSSL_NO_NEXTPROTONEG
  /*
   * call-seq:
   *    ssl.npn_protocol => String | nil
   *
   * Returns the protocol string that was finally selected by the client
   * during the handshake.
   */
  static VALUE
  ossl_ssl_npn_protocol(VALUE self)
  {
      SSL *ssl;
      const unsigned char *out;
      unsigned int outlen;
  
      GetSSL(self, ssl);
  
      SSL_get0_next_proto_negotiated(ssl, &out, &outlen);
      if (!outlen)
  	return Qnil;
      else
  	return rb_str_new((const char *) out, outlen);
  }
  # endif
  
  # ifdef HAVE_SSL_CTX_SET_ALPN_SELECT_CB
  /*
   * call-seq:
   *    ssl.alpn_protocol => String | nil
   *
   * Returns the ALPN protocol string that was finally selected by the server
   * during the handshake.
   */
  static VALUE
  ossl_ssl_alpn_protocol(VALUE self)
  {
      SSL *ssl;
      const unsigned char *out;
      unsigned int outlen;
  
      GetSSL(self, ssl);
  
      SSL_get0_alpn_selected(ssl, &out, &outlen);
      if (!outlen)
  	return Qnil;
      else
  	return rb_str_new((const char *) out, outlen);
  }
  # endif
  
  # ifdef HAVE_SSL_GET_SERVER_TMP_KEY
  /*
   * call-seq:
   *    ssl.tmp_key => PKey or nil
   *
   * Returns the ephemeral key used in case of forward secrecy cipher.
   */
  static VALUE
  ossl_ssl_tmp_key(VALUE self)
  {
      SSL *ssl;
      EVP_PKEY *key;
  
      GetSSL(self, ssl);
      if (!SSL_get_server_tmp_key(ssl, &key))
  	return Qnil;
      return ossl_pkey_new(key);
  }
  # endif /* defined(HAVE_SSL_GET_SERVER_TMP_KEY) */
  #endif /* !defined(OPENSSL_NO_SOCK) */
  
  #undef rb_intern
  #define rb_intern(s) rb_intern_const(s)
  void
  Init_ossl_ssl(void)
  {
  #if 0
      mOSSL = rb_define_module("OpenSSL");
      eOSSLError = rb_define_class_under(mOSSL, "OpenSSLError", rb_eStandardError);
      rb_mWaitReadable = rb_define_module_under(rb_cIO, "WaitReadable");
      rb_mWaitWritable = rb_define_module_under(rb_cIO, "WaitWritable");
  #endif
  
      id_call = rb_intern("call");
      ID_callback_state = rb_intern("callback_state");
  
      ossl_ssl_ex_vcb_idx = SSL_get_ex_new_index(0, (void *)"ossl_ssl_ex_vcb_idx", 0, 0, 0);
      if (ossl_ssl_ex_vcb_idx < 0)
  	ossl_raise(rb_eRuntimeError, "SSL_get_ex_new_index");
      ossl_ssl_ex_ptr_idx = SSL_get_ex_new_index(0, (void *)"ossl_ssl_ex_ptr_idx", 0, 0, 0);
      if (ossl_ssl_ex_ptr_idx < 0)
  	ossl_raise(rb_eRuntimeError, "SSL_get_ex_new_index");
      ossl_sslctx_ex_ptr_idx = SSL_CTX_get_ex_new_index(0, (void *)"ossl_sslctx_ex_ptr_idx", 0, 0, 0);
      if (ossl_sslctx_ex_ptr_idx < 0)
  	ossl_raise(rb_eRuntimeError, "SSL_CTX_get_ex_new_index");
  #if !defined(HAVE_X509_STORE_UP_REF)
      ossl_sslctx_ex_store_p = SSL_CTX_get_ex_new_index(0, (void *)"ossl_sslctx_ex_store_p", 0, 0, 0);
      if (ossl_sslctx_ex_store_p < 0)
  	ossl_raise(rb_eRuntimeError, "SSL_CTX_get_ex_new_index");
  #endif
  
      /* Document-module: OpenSSL::SSL
       *
       * Use SSLContext to set up the parameters for a TLS (former SSL)
       * connection. Both client and server TLS connections are supported,
       * SSLSocket and SSLServer may be used in conjunction with an instance
       * of SSLContext to set up connections.
       */
      mSSL = rb_define_module_under(mOSSL, "SSL");
  
      /* Document-module: OpenSSL::ExtConfig
       *
       * This module contains configuration information about the SSL extension,
       * for example if socket support is enabled, or the host name TLS extension
       * is enabled.  Constants in this module will always be defined, but contain
       * +true+ or +false+ values depending on the configuration of your OpenSSL
       * installation.
       */
      mSSLExtConfig = rb_define_module_under(mOSSL, "ExtConfig");
  
      /* Document-class: OpenSSL::SSL::SSLError
       *
       * Generic error class raised by SSLSocket and SSLContext.
       */
      eSSLError = rb_define_class_under(mSSL, "SSLError", eOSSLError);
      eSSLErrorWaitReadable = rb_define_class_under(mSSL, "SSLErrorWaitReadable", eSSLError);
      rb_include_module(eSSLErrorWaitReadable, rb_mWaitReadable);
      eSSLErrorWaitWritable = rb_define_class_under(mSSL, "SSLErrorWaitWritable", eSSLError);
      rb_include_module(eSSLErrorWaitWritable, rb_mWaitWritable);
  
      Init_ossl_ssl_session();
  
      /* Document-class: OpenSSL::SSL::SSLContext
       *
       * An SSLContext is used to set various options regarding certificates,
       * algorithms, verification, session caching, etc.  The SSLContext is
       * used to create an SSLSocket.
       *
       * All attributes must be set before creating an SSLSocket as the
       * SSLContext will be frozen afterward.
       */
      cSSLContext = rb_define_class_under(mSSL, "SSLContext", rb_cObject);
      rb_define_alloc_func(cSSLContext, ossl_sslctx_s_alloc);
      rb_undef_method(cSSLContext, "initialize_copy");
  
      /*
       * Context certificate
       *
       * The _cert_, _key_, and _extra_chain_cert_ attributes are deprecated.
       * It is recommended to use #add_certificate instead.
       */
      rb_attr(cSSLContext, rb_intern("cert"), 1, 1, Qfalse);
  
      /*
       * Context private key
       *
       * The _cert_, _key_, and _extra_chain_cert_ attributes are deprecated.
       * It is recommended to use #add_certificate instead.
       */
      rb_attr(cSSLContext, rb_intern("key"), 1, 1, Qfalse);
  
      /*
       * A certificate or Array of certificates that will be sent to the client.
       */
      rb_attr(cSSLContext, rb_intern("client_ca"), 1, 1, Qfalse);
  
      /*
       * The path to a file containing a PEM-format CA certificate
       */
      rb_attr(cSSLContext, rb_intern("ca_file"), 1, 1, Qfalse);
  
      /*
       * The path to a directory containing CA certificates in PEM format.
       *
       * Files are looked up by subject's X509 name's hash value.
       */
      rb_attr(cSSLContext, rb_intern("ca_path"), 1, 1, Qfalse);
  
      /*
       * Maximum session lifetime in seconds.
       */
      rb_attr(cSSLContext, rb_intern("timeout"), 1, 1, Qfalse);
  
      /*
       * Session verification mode.
       *
       * Valid modes are VERIFY_NONE, VERIFY_PEER, VERIFY_CLIENT_ONCE,
       * VERIFY_FAIL_IF_NO_PEER_CERT and defined on OpenSSL::SSL
       *
       * The default mode is VERIFY_NONE, which does not perform any verification
       * at all.
       *
       * See SSL_CTX_set_verify(3) for details.
       */
      rb_attr(cSSLContext, rb_intern("verify_mode"), 1, 1, Qfalse);
  
      /*
       * Number of CA certificates to walk when verifying a certificate chain.
       */
      rb_attr(cSSLContext, rb_intern("verify_depth"), 1, 1, Qfalse);
  
      /*
       * A callback for additional certificate verification.  The callback is
       * invoked for each certificate in the chain.
       *
       * The callback is invoked with two values.  _preverify_ok_ indicates
       * indicates if the verification was passed (+true+) or not (+false+).
       * _store_context_ is an OpenSSL::X509::StoreContext containing the
       * context used for certificate verification.
       *
       * If the callback returns +false+, the chain verification is immediately
       * stopped and a bad_certificate alert is then sent.
       */
      rb_attr(cSSLContext, rb_intern("verify_callback"), 1, 1, Qfalse);
  
      /*
       * Whether to check the server certificate is valid for the hostname.
       *
       * In order to make this work, verify_mode must be set to VERIFY_PEER and
       * the server hostname must be given by OpenSSL::SSL::SSLSocket#hostname=.
       */
      rb_attr(cSSLContext, rb_intern("verify_hostname"), 1, 1, Qfalse);
  
      /*
       * An OpenSSL::X509::Store used for certificate verification.
       */
      rb_attr(cSSLContext, rb_intern("cert_store"), 1, 1, Qfalse);
  
      /*
       * An Array of extra X509 certificates to be added to the certificate
       * chain.
       *
       * The _cert_, _key_, and _extra_chain_cert_ attributes are deprecated.
       * It is recommended to use #add_certificate instead.
       */
      rb_attr(cSSLContext, rb_intern("extra_chain_cert"), 1, 1, Qfalse);
  
      /*
       * A callback invoked when a client certificate is requested by a server
       * and no certificate has been set.
       *
       * The callback is invoked with a Session and must return an Array
       * containing an OpenSSL::X509::Certificate and an OpenSSL::PKey.  If any
       * other value is returned the handshake is suspended.
       */
      rb_attr(cSSLContext, rb_intern("client_cert_cb"), 1, 1, Qfalse);
  
      /*
       * Sets the context in which a session can be reused.  This allows
       * sessions for multiple applications to be distinguished, for example, by
       * name.
       */
      rb_attr(cSSLContext, rb_intern("session_id_context"), 1, 1, Qfalse);
  
      /*
       * A callback invoked on a server when a session is proposed by the client
       * but the session could not be found in the server's internal cache.
       *
       * The callback is invoked with the SSLSocket and session id.  The
       * callback may return a Session from an external cache.
       */
      rb_attr(cSSLContext, rb_intern("session_get_cb"), 1, 1, Qfalse);
  
      /*
       * A callback invoked when a new session was negotiated.
       *
       * The callback is invoked with an SSLSocket.  If +false+ is returned the
       * session will be removed from the internal cache.
       */
      rb_attr(cSSLContext, rb_intern("session_new_cb"), 1, 1, Qfalse);
  
      /*
       * A callback invoked when a session is removed from the internal cache.
       *
       * The callback is invoked with an SSLContext and a Session.
       *
       * IMPORTANT NOTE: It is currently not possible to use this safely in a
       * multi-threaded application. The callback is called inside a global lock
       * and it can randomly cause deadlock on Ruby thread switching.
       */
      rb_attr(cSSLContext, rb_intern("session_remove_cb"), 1, 1, Qfalse);
  
      rb_define_const(mSSLExtConfig, "HAVE_TLSEXT_HOST_NAME", Qtrue);
  
      /*
       * A callback invoked whenever a new handshake is initiated on an
       * established connection. May be used to disable renegotiation entirely.
       *
       * The callback is invoked with the active SSLSocket. The callback's
       * return value is ignored. A normal return indicates "approval" of the
       * renegotiation and will continue the process. To forbid renegotiation
       * and to cancel the process, raise an exception within the callback.
       *
       * === Disable client renegotiation
       *
       * When running a server, it is often desirable to disable client
       * renegotiation entirely. You may use a callback as follows to implement
       * this feature:
       *
       *   ctx.renegotiation_cb = lambda do |ssl|
       *     raise RuntimeError, "Client renegotiation disabled"
       *   end
       */
      rb_attr(cSSLContext, rb_intern("renegotiation_cb"), 1, 1, Qfalse);
  #ifndef OPENSSL_NO_NEXTPROTONEG
      /*
       * An Enumerable of Strings. Each String represents a protocol to be
       * advertised as the list of supported protocols for Next Protocol
       * Negotiation. Supported in OpenSSL 1.0.1 and higher. Has no effect
       * on the client side. If not set explicitly, the NPN extension will
       * not be sent by the server in the handshake.
       *
       * === Example
       *
       *   ctx.npn_protocols = ["http/1.1", "spdy/2"]
       */
      rb_attr(cSSLContext, rb_intern("npn_protocols"), 1, 1, Qfalse);
      /*
       * A callback invoked on the client side when the client needs to select
       * a protocol from the list sent by the server. Supported in OpenSSL 1.0.1
       * and higher. The client MUST select a protocol of those advertised by
       * the server. If none is acceptable, raising an error in the callback
       * will cause the handshake to fail. Not setting this callback explicitly
       * means not supporting the NPN extension on the client - any protocols
       * advertised by the server will be ignored.
       *
       * === Example
       *
       *   ctx.npn_select_cb = lambda do |protocols|
       *     # inspect the protocols and select one
       *     protocols.first
       *   end
       */
      rb_attr(cSSLContext, rb_intern("npn_select_cb"), 1, 1, Qfalse);
  #endif
  
  #ifdef HAVE_SSL_CTX_SET_ALPN_SELECT_CB
      /*
       * An Enumerable of Strings. Each String represents a protocol to be
       * advertised as the list of supported protocols for Application-Layer
       * Protocol Negotiation. Supported in OpenSSL 1.0.2 and higher. Has no
       * effect on the server side. If not set explicitly, the ALPN extension will
       * not be included in the handshake.
       *
       * === Example
       *
       *   ctx.alpn_protocols = ["http/1.1", "spdy/2", "h2"]
       */
      rb_attr(cSSLContext, rb_intern("alpn_protocols"), 1, 1, Qfalse);
      /*
       * A callback invoked on the server side when the server needs to select
       * a protocol from the list sent by the client. Supported in OpenSSL 1.0.2
       * and higher. The callback must return a protocol of those advertised by
       * the client. If none is acceptable, raising an error in the callback
       * will cause the handshake to fail. Not setting this callback explicitly
       * means not supporting the ALPN extension on the server - any protocols
       * advertised by the client will be ignored.
       *
       * === Example
       *
       *   ctx.alpn_select_cb = lambda do |protocols|
       *     # inspect the protocols and select one
       *     protocols.first
       *   end
       */
      rb_attr(cSSLContext, rb_intern("alpn_select_cb"), 1, 1, Qfalse);
  #endif
  
      rb_define_alias(cSSLContext, "ssl_timeout", "timeout");
      rb_define_alias(cSSLContext, "ssl_timeout=", "timeout=");
      rb_define_private_method(cSSLContext, "set_minmax_proto_version",
  			     ossl_sslctx_set_minmax_proto_version, 2);
      rb_define_method(cSSLContext, "ciphers",     ossl_sslctx_get_ciphers, 0);
      rb_define_method(cSSLContext, "ciphers=",    ossl_sslctx_set_ciphers, 1);
      rb_define_method(cSSLContext, "ecdh_curves=", ossl_sslctx_set_ecdh_curves, 1);
      rb_define_method(cSSLContext, "security_level", ossl_sslctx_get_security_level, 0);
      rb_define_method(cSSLContext, "security_level=", ossl_sslctx_set_security_level, 1);
  #ifdef SSL_MODE_SEND_FALLBACK_SCSV
      rb_define_method(cSSLContext, "enable_fallback_scsv", ossl_sslctx_enable_fallback_scsv, 0);
  #endif
      rb_define_method(cSSLContext, "add_certificate", ossl_sslctx_add_certificate, -1);
  
      rb_define_method(cSSLContext, "setup", ossl_sslctx_setup, 0);
      rb_define_alias(cSSLContext, "freeze", "setup");
  
      /*
       * No session caching for client or server
       */
      rb_define_const(cSSLContext, "SESSION_CACHE_OFF", LONG2NUM(SSL_SESS_CACHE_OFF));
  
      /*
       * Client sessions are added to the session cache
       */
      rb_define_const(cSSLContext, "SESSION_CACHE_CLIENT", LONG2NUM(SSL_SESS_CACHE_CLIENT)); /* doesn't actually do anything in 0.9.8e */
  
      /*
       * Server sessions are added to the session cache
       */
      rb_define_const(cSSLContext, "SESSION_CACHE_SERVER", LONG2NUM(SSL_SESS_CACHE_SERVER));
  
      /*
       * Both client and server sessions are added to the session cache
       */
      rb_define_const(cSSLContext, "SESSION_CACHE_BOTH", LONG2NUM(SSL_SESS_CACHE_BOTH)); /* no different than CACHE_SERVER in 0.9.8e */
  
      /*
       * Normally the session cache is checked for expired sessions every 255
       * connections.  Since this may lead to a delay that cannot be controlled,
       * the automatic flushing may be disabled and #flush_sessions can be
       * called explicitly.
       */
      rb_define_const(cSSLContext, "SESSION_CACHE_NO_AUTO_CLEAR", LONG2NUM(SSL_SESS_CACHE_NO_AUTO_CLEAR));
  
      /*
       * Always perform external lookups of sessions even if they are in the
       * internal cache.
       *
       * This flag has no effect on clients
       */
      rb_define_const(cSSLContext, "SESSION_CACHE_NO_INTERNAL_LOOKUP", LONG2NUM(SSL_SESS_CACHE_NO_INTERNAL_LOOKUP));
  
      /*
       * Never automatically store sessions in the internal store.
       */
      rb_define_const(cSSLContext, "SESSION_CACHE_NO_INTERNAL_STORE", LONG2NUM(SSL_SESS_CACHE_NO_INTERNAL_STORE));
  
      /*
       * Enables both SESSION_CACHE_NO_INTERNAL_LOOKUP and
       * SESSION_CACHE_NO_INTERNAL_STORE.
       */
      rb_define_const(cSSLContext, "SESSION_CACHE_NO_INTERNAL", LONG2NUM(SSL_SESS_CACHE_NO_INTERNAL));
  
      rb_define_method(cSSLContext, "session_add",     ossl_sslctx_session_add, 1);
      rb_define_method(cSSLContext, "session_remove",     ossl_sslctx_session_remove, 1);
      rb_define_method(cSSLContext, "session_cache_mode",     ossl_sslctx_get_session_cache_mode, 0);
      rb_define_method(cSSLContext, "session_cache_mode=",     ossl_sslctx_set_session_cache_mode, 1);
      rb_define_method(cSSLContext, "session_cache_size",     ossl_sslctx_get_session_cache_size, 0);
      rb_define_method(cSSLContext, "session_cache_size=",     ossl_sslctx_set_session_cache_size, 1);
      rb_define_method(cSSLContext, "session_cache_stats",     ossl_sslctx_get_session_cache_stats, 0);
      rb_define_method(cSSLContext, "flush_sessions",     ossl_sslctx_flush_sessions, -1);
      rb_define_method(cSSLContext, "options",     ossl_sslctx_get_options, 0);
      rb_define_method(cSSLContext, "options=",     ossl_sslctx_set_options, 1);
  
      /*
       * Document-class: OpenSSL::SSL::SSLSocket
       */
      cSSLSocket = rb_define_class_under(mSSL, "SSLSocket", rb_cObject);
  #ifdef OPENSSL_NO_SOCK
      rb_define_const(mSSLExtConfig, "OPENSSL_NO_SOCK", Qtrue);
      rb_define_method(cSSLSocket, "initialize", rb_f_notimplement, -1);
  #else
      rb_define_const(mSSLExtConfig, "OPENSSL_NO_SOCK", Qfalse);
      rb_define_alloc_func(cSSLSocket, ossl_ssl_s_alloc);
      rb_define_method(cSSLSocket, "initialize", ossl_ssl_initialize, -1);
      rb_undef_method(cSSLSocket, "initialize_copy");
      rb_define_method(cSSLSocket, "connect",    ossl_ssl_connect, 0);
      rb_define_method(cSSLSocket, "connect_nonblock",    ossl_ssl_connect_nonblock, -1);
      rb_define_method(cSSLSocket, "accept",     ossl_ssl_accept, 0);
      rb_define_method(cSSLSocket, "accept_nonblock", ossl_ssl_accept_nonblock, -1);
      rb_define_method(cSSLSocket, "sysread",    ossl_ssl_read, -1);
      rb_define_private_method(cSSLSocket, "sysread_nonblock",    ossl_ssl_read_nonblock, -1);
      rb_define_method(cSSLSocket, "syswrite",   ossl_ssl_write, 1);
      rb_define_private_method(cSSLSocket, "syswrite_nonblock",    ossl_ssl_write_nonblock, -1);
      rb_define_private_method(cSSLSocket, "stop",   ossl_ssl_stop, 0);
      rb_define_method(cSSLSocket, "cert",       ossl_ssl_get_cert, 0);
      rb_define_method(cSSLSocket, "peer_cert",  ossl_ssl_get_peer_cert, 0);
      rb_define_method(cSSLSocket, "peer_cert_chain", ossl_ssl_get_peer_cert_chain, 0);
      rb_define_method(cSSLSocket, "ssl_version",    ossl_ssl_get_version, 0);
      rb_define_method(cSSLSocket, "cipher",     ossl_ssl_get_cipher, 0);
      rb_define_method(cSSLSocket, "state",      ossl_ssl_get_state, 0);
      rb_define_method(cSSLSocket, "pending",    ossl_ssl_pending, 0);
      rb_define_method(cSSLSocket, "session_reused?",    ossl_ssl_session_reused, 0);
      /* implementation of OpenSSL::SSL::SSLSocket#session is in lib/openssl/ssl.rb */
      rb_define_method(cSSLSocket, "session=",    ossl_ssl_set_session, 1);
      rb_define_method(cSSLSocket, "verify_result", ossl_ssl_get_verify_result, 0);
      rb_define_method(cSSLSocket, "client_ca", ossl_ssl_get_client_ca_list, 0);
      /* #hostname is defined in lib/openssl/ssl.rb */
      rb_define_method(cSSLSocket, "hostname=", ossl_ssl_set_hostname, 1);
      rb_define_method(cSSLSocket, "finished_message", ossl_ssl_get_finished, 0);
      rb_define_method(cSSLSocket, "peer_finished_message", ossl_ssl_get_peer_finished, 0);
  # ifdef HAVE_SSL_GET_SERVER_TMP_KEY
      rb_define_method(cSSLSocket, "tmp_key", ossl_ssl_tmp_key, 0);
  # endif
  # ifdef HAVE_SSL_CTX_SET_ALPN_SELECT_CB
      rb_define_method(cSSLSocket, "alpn_protocol", ossl_ssl_alpn_protocol, 0);
  # endif
  # ifndef OPENSSL_NO_NEXTPROTONEG
      rb_define_method(cSSLSocket, "npn_protocol", ossl_ssl_npn_protocol, 0);
  # endif
  #endif
  
      rb_define_const(mSSL, "VERIFY_NONE", INT2NUM(SSL_VERIFY_NONE));
      rb_define_const(mSSL, "VERIFY_PEER", INT2NUM(SSL_VERIFY_PEER));
      rb_define_const(mSSL, "VERIFY_FAIL_IF_NO_PEER_CERT", INT2NUM(SSL_VERIFY_FAIL_IF_NO_PEER_CERT));
      rb_define_const(mSSL, "VERIFY_CLIENT_ONCE", INT2NUM(SSL_VERIFY_CLIENT_ONCE));
  
      rb_define_const(mSSL, "OP_ALL", ULONG2NUM(SSL_OP_ALL));
      rb_define_const(mSSL, "OP_LEGACY_SERVER_CONNECT", ULONG2NUM(SSL_OP_LEGACY_SERVER_CONNECT));
  #ifdef SSL_OP_TLSEXT_PADDING /* OpenSSL 1.0.1h and OpenSSL 1.0.2 */
      rb_define_const(mSSL, "OP_TLSEXT_PADDING", ULONG2NUM(SSL_OP_TLSEXT_PADDING));
  #endif
  #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG /* OpenSSL 1.0.1f and OpenSSL 1.0.2 */
      rb_define_const(mSSL, "OP_SAFARI_ECDHE_ECDSA_BUG", ULONG2NUM(SSL_OP_SAFARI_ECDHE_ECDSA_BUG));
  #endif
  #ifdef SSL_OP_ALLOW_NO_DHE_KEX /* OpenSSL 1.1.1 */
      rb_define_const(mSSL, "OP_ALLOW_NO_DHE_KEX", ULONG2NUM(SSL_OP_ALLOW_NO_DHE_KEX));
  #endif
      rb_define_const(mSSL, "OP_DONT_INSERT_EMPTY_FRAGMENTS", ULONG2NUM(SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS));
      rb_define_const(mSSL, "OP_NO_TICKET", ULONG2NUM(SSL_OP_NO_TICKET));
      rb_define_const(mSSL, "OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION", ULONG2NUM(SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION));
      rb_define_const(mSSL, "OP_NO_COMPRESSION", ULONG2NUM(SSL_OP_NO_COMPRESSION));
      rb_define_const(mSSL, "OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION", ULONG2NUM(SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION));
  #ifdef SSL_OP_NO_ENCRYPT_THEN_MAC /* OpenSSL 1.1.1 */
      rb_define_const(mSSL, "OP_NO_ENCRYPT_THEN_MAC", ULONG2NUM(SSL_OP_NO_ENCRYPT_THEN_MAC));
  #endif
      rb_define_const(mSSL, "OP_CIPHER_SERVER_PREFERENCE", ULONG2NUM(SSL_OP_CIPHER_SERVER_PREFERENCE));
      rb_define_const(mSSL, "OP_TLS_ROLLBACK_BUG", ULONG2NUM(SSL_OP_TLS_ROLLBACK_BUG));
  #ifdef SSL_OP_NO_RENEGOTIATION /* OpenSSL 1.1.1 */
      rb_define_const(mSSL, "OP_NO_RENEGOTIATION", ULONG2NUM(SSL_OP_NO_RENEGOTIATION));
  #endif
      rb_define_const(mSSL, "OP_CRYPTOPRO_TLSEXT_BUG", ULONG2NUM(SSL_OP_CRYPTOPRO_TLSEXT_BUG));
  
      rb_define_const(mSSL, "OP_NO_SSLv3", ULONG2NUM(SSL_OP_NO_SSLv3));
      rb_define_const(mSSL, "OP_NO_TLSv1", ULONG2NUM(SSL_OP_NO_TLSv1));
      rb_define_const(mSSL, "OP_NO_TLSv1_1", ULONG2NUM(SSL_OP_NO_TLSv1_1));
      rb_define_const(mSSL, "OP_NO_TLSv1_2", ULONG2NUM(SSL_OP_NO_TLSv1_2));
  #ifdef SSL_OP_NO_TLSv1_3 /* OpenSSL 1.1.1 */
      rb_define_const(mSSL, "OP_NO_TLSv1_3", ULONG2NUM(SSL_OP_NO_TLSv1_3));
  #endif
  
      /* SSL_OP_* flags for DTLS */
  #if 0
      rb_define_const(mSSL, "OP_NO_QUERY_MTU", ULONG2NUM(SSL_OP_NO_QUERY_MTU));
      rb_define_const(mSSL, "OP_COOKIE_EXCHANGE", ULONG2NUM(SSL_OP_COOKIE_EXCHANGE));
      rb_define_const(mSSL, "OP_CISCO_ANYCONNECT", ULONG2NUM(SSL_OP_CISCO_ANYCONNECT));
  #endif
  
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_MICROSOFT_SESS_ID_BUG", ULONG2NUM(SSL_OP_MICROSOFT_SESS_ID_BUG));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_NETSCAPE_CHALLENGE_BUG", ULONG2NUM(SSL_OP_NETSCAPE_CHALLENGE_BUG));
      /* Deprecated in OpenSSL 0.9.8q and 1.0.0c. */
      rb_define_const(mSSL, "OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG", ULONG2NUM(SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG));
      /* Deprecated in OpenSSL 1.0.1h and 1.0.2. */
      rb_define_const(mSSL, "OP_SSLREF2_REUSE_CERT_TYPE_BUG", ULONG2NUM(SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_MICROSOFT_BIG_SSLV3_BUFFER", ULONG2NUM(SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER));
      /* Deprecated in OpenSSL 0.9.7h and 0.9.8b. */
      rb_define_const(mSSL, "OP_MSIE_SSLV2_RSA_PADDING", ULONG2NUM(SSL_OP_MSIE_SSLV2_RSA_PADDING));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_SSLEAY_080_CLIENT_DH_BUG", ULONG2NUM(SSL_OP_SSLEAY_080_CLIENT_DH_BUG));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_TLS_D5_BUG", ULONG2NUM(SSL_OP_TLS_D5_BUG));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_TLS_BLOCK_PADDING_BUG", ULONG2NUM(SSL_OP_TLS_BLOCK_PADDING_BUG));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_SINGLE_ECDH_USE", ULONG2NUM(SSL_OP_SINGLE_ECDH_USE));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_SINGLE_DH_USE", ULONG2NUM(SSL_OP_SINGLE_DH_USE));
      /* Deprecated in OpenSSL 1.0.1k and 1.0.2. */
      rb_define_const(mSSL, "OP_EPHEMERAL_RSA", ULONG2NUM(SSL_OP_EPHEMERAL_RSA));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_NO_SSLv2", ULONG2NUM(SSL_OP_NO_SSLv2));
      /* Deprecated in OpenSSL 1.0.1. */
      rb_define_const(mSSL, "OP_PKCS1_CHECK_1", ULONG2NUM(SSL_OP_PKCS1_CHECK_1));
      /* Deprecated in OpenSSL 1.0.1. */
      rb_define_const(mSSL, "OP_PKCS1_CHECK_2", ULONG2NUM(SSL_OP_PKCS1_CHECK_2));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_NETSCAPE_CA_DN_BUG", ULONG2NUM(SSL_OP_NETSCAPE_CA_DN_BUG));
      /* Deprecated in OpenSSL 1.1.0. */
      rb_define_const(mSSL, "OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG", ULONG2NUM(SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG));
  
  
      /*
       * SSL/TLS version constants. Used by SSLContext#min_version= and
       * #max_version=
       */
      /* SSL 2.0 */
      rb_define_const(mSSL, "SSL2_VERSION", INT2NUM(SSL2_VERSION));
      /* SSL 3.0 */
      rb_define_const(mSSL, "SSL3_VERSION", INT2NUM(SSL3_VERSION));
      /* TLS 1.0 */
      rb_define_const(mSSL, "TLS1_VERSION", INT2NUM(TLS1_VERSION));
      /* TLS 1.1 */
      rb_define_const(mSSL, "TLS1_1_VERSION", INT2NUM(TLS1_1_VERSION));
      /* TLS 1.2 */
      rb_define_const(mSSL, "TLS1_2_VERSION", INT2NUM(TLS1_2_VERSION));
  #ifdef TLS1_3_VERSION /* OpenSSL 1.1.1 */
      /* TLS 1.3 */
      rb_define_const(mSSL, "TLS1_3_VERSION", INT2NUM(TLS1_3_VERSION));
  #endif
  
  
      sym_exception = ID2SYM(rb_intern("exception"));
      sym_wait_readable = ID2SYM(rb_intern("wait_readable"));
      sym_wait_writable = ID2SYM(rb_intern("wait_writable"));
  
      id_tmp_dh_callback = rb_intern("tmp_dh_callback");
      id_npn_protocols_encoded = rb_intern("npn_protocols_encoded");
  
  #define DefIVarID(name) do \
      id_i_##name = rb_intern("@"#name); while (0)
  
      DefIVarID(cert_store);
      DefIVarID(ca_file);
      DefIVarID(ca_path);
      DefIVarID(verify_mode);
      DefIVarID(verify_depth);
      DefIVarID(verify_callback);
      DefIVarID(client_ca);
      DefIVarID(renegotiation_cb);
      DefIVarID(cert);
      DefIVarID(key);
      DefIVarID(extra_chain_cert);
      DefIVarID(client_cert_cb);
      DefIVarID(timeout);
      DefIVarID(session_id_context);
      DefIVarID(session_get_cb);
      DefIVarID(session_new_cb);
      DefIVarID(session_remove_cb);
      DefIVarID(npn_select_cb);
      DefIVarID(npn_protocols);
      DefIVarID(alpn_protocols);
      DefIVarID(alpn_select_cb);
      DefIVarID(servername_cb);
      DefIVarID(verify_hostname);
  
      DefIVarID(io);
      DefIVarID(context);
      DefIVarID(hostname);
  }
  